President Joe Biden pledged Wednesday that western allies “will not waver” in defense of Ukraine, casting the struggle against Russian aggression as one of the world's central challenges requiring a broad coalition of countries to stand in defense of freedom.

“Our unity will not falter," Biden declared. "I promise you.”

He made the promise at the NATO summit in the capital of Lithuania, a country that he said knows the “transformational power of freedom" after spending decades under Moscow's thumb. He drew parallels between Lithuania's struggle to escape Soviet rule and Ukraine's ongoing fight to repel Russia's deadly invasion, highlighting the importance of rallying allies to take on the challenge.

“America never recognized the Soviet occupation of the Baltic," he said to an outpouring of cheers from a crowd of thousands in a courtyard at Vilnius University draped with American and Lithuanian flags. "Never, never.” More spectators gathered in an overflow area, where a big screen was set up.

Biden spent two days in Vilnius for the annual NATO summit, where members of the western military alliance pledged more support for Ukraine but stopped short of extending an invitation for the besieged country to join the alliance. After meeting with Ukrainian President Volodymyr Zelenskyy, who entered the summit demanding a clear path for his country toward joining the alliance, something that was initially promised back in 2008, Biden said that other security guarantees agreed to at the summit will be even more significant.

“One thing Zelenskyy understands now is that whether or not he’s in NATO now, it’s not relevant as long as he has commitments," Biden said, comparing the situation to how the U.S. ensures Israel's security edge over its neighbors.

The president pointed to the U.S. and allied response to Moscow's invasion as a model for how to respond to other global challenges, from climate change to the rise of China, saying nations' positions are stronger when they “build the broadest and deepest coalition.”

“Our commitment to Ukraine will not weaken,” he said. “We will stand for freedom today, tomorrow and for as long as it takes.”

The president was headed next to Finland, the newest member of NATO, for a meeting of Nordic leaders. During his speech, Biden hailed an agreement to advance Sweden's membership in NATO after Turkish President Recep Tayyip Erdogan agreed to drop his objections.

"President Erdogan kept his word," Biden said, clearing a path for the alliance to have 32 members.

The U.S. president's enthusiasm for expanding NATO has not extended to Ukraine. He's expressed concerns about the country's readiness to join the alliance, as well as fears that the West could be drawn into a wider conflict with Russia.

The competing priorities in the midst of Europe’s bloodiest war in generations created an undercurrent of friction even as Biden and Zelenskyy projected a united front when they met earlier Wednesday. Their public encounter had the vibe of two leaders clearing the air, and each conspicuously heaped praise on his counterpart.

Biden lauded Zelenskyy and Ukrainians for their courage by saying it's “been a model for the whole world to see.” Zelenskyy thanked Biden and the American people for billions of dollars in military assistance, saying that “you spend this money for our lives.”

Wearing a blue-and-yellow-striped tie in the colors of the Ukrainian flag, Biden acknowledged that Zelenskyy has occasionally been unsatisfied by unfulfilled requests for weapons.

“The frustration, I can only imagine," Biden said. "I know that you're many times frustrated about whether things get to you quickly enough, what's getting to you and how we're getting it. But I promise you, the United States is doing everything we can to get you what you need.”

Biden also said the war had created a sense of unity about opposing international aggression.

“It’s bringing the world together," he said. "It’s a hell of a price to pay, but it’s bringing the world together.”

The meeting came after a few other encounters between Biden and Zelenskyy at the summit. They sat close to each other at the inaugural meeting of the NATO-Ukraine Council, a new forum that's intended to give Kyiv a greater voice within the alliance.

And they shared the stage as the Group of Seven, which includes the world's most powerful democratic countries, announced plans for long-term security assistance for Ukraine.

But Wednesday afternoon was the first opportunity for Biden and Zelenskyy to sit down privately with their advisers after their public comments.

And by then, Zelenskyy had softened his tone considerably. En route to Vilnius on Tuesday, he had blasted NATO's vague plans for Ukraine's eventual membership, tweeting, “It’s unprecedented and absurd when a time frame is set neither for the invitation nor for Ukraine’s membership.”

Jake Sullivan, Biden’s national security adviser, said everyone “needs to look squarely at the fact” that allowing Ukraine to join NATO at this point “means war with Russia.”

“That is an inescapable fact,” he told CNN.

Sullivan credited Biden with ensuring that NATO is “more unified and more determined and more decisive than at any point.”

“That’s President Biden’s legacy when it comes to NATO, and it’s one that he can be very proud of," he said.

In an interview with The Associated Press before Biden left on his trip, Senate Minority Leader Mitch McConnell said the president has been “heading in the right direction but not fast enough” when it comes to supporting Ukraine.

“The weapons transfers never seem to happen as soon as they’re announced,” said McConnell, a Kentucky Republican. Although Ukrainians are “extremely grateful for the help,” he said, the assistance "frequently doesn’t get there soon enough to be the most effective.”

Although McConnell has been a firm supporter of sending help to Ukraine, other Republicans have voiced skepticism, creating uncertainty about Biden's ability to make long-term financial commitments.

As the Russian invasion of Ukraine continues with no end in sight, NATO's much-celebrated unity faces fresh strains when leaders gather for their annual summit this week in Vilnius, Lithuania.

Video above: Biden Meets With Swedish Prime Minister in Support of NATO Bid

The world's biggest security alliance is struggling to reach an agreement on admitting Sweden as its 32nd member. Military spending by member nations lags behind long-standing goals. An inability to compromise over who should serve as NATO's next leader forced an extension of the current secretary-general's term for an extra year.

Perhaps the most difficult questions are over how Ukraine should be eased into NATO. Some maintain admitting Ukraine would fulfill a promise made years ago and be a necessary step to deter Russian aggression in Eastern Europe. Others fear it would be seen as a provocation that could spiral into an even wider conflict.

"I don't think it's ready for membership in NATO," President Joe Biden told CNN in an interview airing Sunday. He said joining NATO requires countries to "meet all the qualifications, from democratization to a whole range of other issues."

He said the United States should provide long-term security assistance to Ukraine — "the capacity to defend themselves" — as it does with Israel.

Bickering among friends is not uncommon, and the current catalog of disputes pales in comparison with past fears that Donald Trump would turn his back on the alliance during his presidency. But the current challenges come at a moment when Biden and his counterparts are heavily invested in demonstrating harmony among members.

"Any fissure, any lack of solidarity provides an opportunity for those who would oppose the alliance," said Douglas Lute, U.S. ambassador to NATO under President Barack Obama.

Russian President Vladimir Putin is eager to exploit divisions as he struggles to gain ground in Ukraine and faces political challenges at home, including the aftermath of a brief revolt by the Wagner mercenary group.

"You don't want to present any openings," Lute said. "You don't want to present any gaps or seams."

By some measures, the war in Ukraine has reinvigorated NATO, which was created at the beginning of the Cold War as a bulwark against Moscow. NATO members have poured military hardware into Ukraine to help with its counteroffensive, and Finland ended a history of nonalignment to become NATO's 31st member.

"I think it's appropriate to look at all the success," Senate Republican leader Mitch McConnell of Kentucky told The Associated Press. "So I think the invasion has strengthened NATO — exactly the opposite of what Putin anticipated."

He noted Germany's shift toward a more robust defense policy as well as increase in military spending in other countries.

The latest test of NATO solidarity came Friday with what Biden said was a "difficult decision" to provide cluster munitions to Ukraine. More than two-thirds of alliance members have banned the weapon because it has a track record for causing many civilian casualties. The U.S., Russia and Ukraine are not among the more than 120 countries that have not signed a convention outlawing the use of the bombs.

As for Ukraine's possible entry into NATO, the alliance said in 2008 that Kyiv eventually would become a member. Since then, little action has been taken toward that goal. Putin occupied parts of Ukraine in 2014 and then tried to capture the capital in 2022 with his invasion.

"A gray zone is a green light for Putin," said Daniel Fried, a former U.S. ambassador to Poland who is now a distinguished fellow at the Atlantic Council.

Ukraine's president, Volodymyr Zelenskyy, called for a unified signal from NATO on Ukraine and for his country to join the alliance.

"It would be an important message to say that NATO is not afraid of Russia," Zelenskyy said through a translator in an ABC interview, when asked whether he would come to Vilnius. "Ukraine should get clear security guarantees while it is not in NATO. And that is a very important point. Only under these conditions our meeting would be meaningful. Otherwise, it's just another politics."

The U.S. and Germany insist that the focus should be on supplying weapons and ammunition to Ukraine, rather than taking the more provocative step of extending a formal invitation to join NATO. Countries on NATO's Eastern flank — Estonia, Latvia, Lithuania and Poland — want firmer assurances on future membership.

NATO could decide to elevate its relationship with Ukraine, creating what would be known as the NATO-Ukraine Council and giving Kyiv a seat at the table for consultations.

Also in the spotlight in Vilnius will be Turkish President Recep Tayyip Erdogan, the main obstacle to Sweden's attempts to join NATO alongside neighbor Finland.

Erdogan accuses Sweden of being too lenient on anti-Islamic demonstrations and militant Kurdish groups that have waged a long insurgency in Turkey.

Sweden recently changed its anti-terrorism legislation and lifted an arms embargo on Turkey. But a man burned a Quran outside a mosque in Stockholm last week, and Erdogan signaled that this would pose another hurdle. He equated "those who permitted the crime" to those who perpetrated it.

Turkey and the U.S. are also at an impasse over the sale of F-16 fighter jets. Erdogan wants the upgraded planes, but Biden says Sweden's NATO membership has to be dealt with first. McConnell said in the AP interview that he supports the sale of the fighter jets to Turkey "provided that the membership of Sweden is settled."

It's not the first time that Erdogan has sought to use a NATO summit for Turkish gain. In 2009, he held up the nomination of Anders Fogh Rasmussen as secretary-general but agreed to the move after securing some senior posts for Turkish officials at the alliance.

Max Bergmann, a former State Department official who leads the Europe Program at the Center for Strategic and International Studies, said there's growing frustration among allies toward Erdogan, building on concerns about his ties to Putin, democratic backsliding and sanctions evasion.

"They've tried playing nice," Bergmann said. "The question is whether it's time to get much more confrontational."

Hungary's prime minister, Viktor Orban, is also delaying his country's approval of Sweden's membership. In response, Idaho Sen. Jim Risch, the top Republican on the Senate Foreign Relations Committee, is blocking a $735 million U.S. arms sale to Hungary.

"We don't want members who aren't interested in doing everything possible to strengthen the alliance rather than the pursuit of their own or individual interests," Risch said. "I'm just sick and tired of it."

But he rejected the idea that these disagreements are a sign of weakness within NATO.

"These are kinds of things that always arise in an alliance," he said. "The fact that we've been able to deal with them and will continue to deal with them proves that this is the most successful and strongest military alliance in the history of the world."

At least one potentially difficult issue is off the summit agenda. Rather than seek consensus on a new NATO leader, members agreed to extend the tenure of Jens Stoltenberg, who's held the job since 2014, for a year. It's his fourth extension.

Most members wanted a woman to be the next secretary-general, and Danish Prime Minister Mette Frederiksen had been considered a favorite. But Poland insisted on a candidate from the Baltic states because there had already been two Nordic secretaries general in a row. (Stoltenberg was a Norwegian prime minister and Rasmussen was a Danish prime minister.)

Others are skeptical of accepting a nominee from the Baltics, whose leaders tend to be more provocative in their approach to Russia, including supporting Ukraine's desire to rapidly join NATO.

More disagreements loom over NATO's updated plans for countering any invasion that Russia might launch on allied territory.

___

Cook reported from Brussels. Associated Press writer Sylvie Corbet in Paris contributed to this report.

Bruce Springsteen issued a call for common ground, unity and political centrism in a 2-minute long ad for Jeep set to run during the Super Bowl on Sunday.The ad, featuring wide-shot vistas of the American countryside, open roads and slow-motion shots of "The Boss," centers on a tiny chapel in Lebanon, Kansas, that purportedly sits in the geographical center of the continental United States."All are more than welcome to come meet here in the middle," the "Thunder Road" singer says in a voiceover. "It's no secret the middle has been a hard place to get to lately, between red and blue, between servant and citizen, between our freedom and our fear. PGlmcmFtZSBzdHlsZT0nd2lkdGg6MTAwJTsgaGVpZ2h0OjgwMHB4Oycgc3JjPSJodHRwczovL3d3dy55b3V0dWJlLmNvbS9lbWJlZC9EMlhZSC1JRXZoSSIgZnJhbWVib3JkZXI9IjAiIGFsbG93PSJhY2NlbGVyb21ldGVyOyBhdXRvcGxheTsgY2xpcGJvYXJkLXdyaXRlOyBlbmNyeXB0ZWQtbWVkaWE7IGd5cm9zY29wZTsgcGljdHVyZS1pbi1waWN0dXJlIiBhbGxvd2Z1bGxzY3JlZW4+PC9pZnJhbWU+"Now fear has never been the best of who we are, and as for freedom, it's not the property of just the fortunate few, it belongs to us all. Whoever you are, wherever you're from, it's what connects us, and we need that connection. We need the middle," he says.Ambient music plays throughout the commercial, interspersed by Springsteen's speech. Over the course of the ad, the camera shows Springsteen doing various nondescript activities: writing in a notebook, driving, drinking a hot liquid, rubbing dirt in his hands, opening a door, lighting a candle and putting on a hat."We just have to remember the very soil we stand on is common ground, so we can get there. We can make it to the mountaintop through the desert, and we will cross this divide. Our light has always found its way through the darkness. And there's hope on the road up ahead," Springsteen says.The ad then ends with a dedication: "To the ReUnited States of America."