WASHINGTON (AP) — Secretary of State Antony Blinken said he spoke to Russian Foreign Minister Sergey Lavrov by phone on Friday and urged Moscow to accept a U.S. offer to release WNBA star Brittney Griner and another American detainee, Paul Whelan.

It was Blinken's first talk with his Russian counterpart since before Russia's invasion of Ukraine in February.

Blinken did not provide details of Lavrov’s response to what he had previously called a “substantial proposal." Blinken had publicly requested the call and revealed the existence of the offer to Russia — which people familiar with it say involves a swap for Whelan and Griner with convicted Russian arms dealer Viktor Bout.

Blinken described the call as “a frank and direct conversation” centered primarily on the proposal for the release of the Americans.

“I urged Foreign Minister Lavrov to move forward with that proposal," he said. "I can’t give you an assessment of whether that is any more or less likely.”

Blinken also said he had pressed Lavrov on the importance of Russia following through on an agreement to allow Ukrainian grain shipments to leave the Black Sea and warned him of consequences should Moscow move ahead with suspected plans to annex portions of eastern and southern Ukraine.

Blinken said he told Lavrov that the world will “never recognize” any annexation of Ukrainian territory, which he said would “will result in significant additional costs for Russia.”

He declined to comment on how Lavrov replied to his messages.

“I don’t want to characterize any of Foreign Minister Lavrov’s responses," he stated.

WNBA All-Star Brittney Griner was arrested last month at a Moscow airport after Russian authorities said a search of her luggage revealed vape cartridges.

The Russian Customs Service said Saturday that the cartridges were identified as containing oil derived from cannabis, which could carry a maximum penalty of 10 years in prison. The customs service identified the person arrested as a player for the U.S. women's team and did not specify the date of her arrest. Russian media reported the player was Griner, and her agent, Lindsay Kagawa Colas, did not dispute those reports.

"We are aware of the situation with Brittney Griner in Russia and are in close contact with her, her legal representation in Russia, her family, her teams, and the WNBA and NBA," Kagawa Colas said Saturday. "As this is an ongoing legal matter, we are not able to comment further on the specifics of her case but can confirm that as we work to get her home, her mental and physical health remain our primary concern."

On Saturday, the State Department issued a "do not travel" advisory for Russia because of its invasion of Ukraine and urged all U.S. citizens to depart immediately, citing factors including "the potential for harassment against U.S. citizens by Russian government security officials" and "the Embassy’s limited ability to assist" Americans in Russia.

Griner, who plays for the WNBA's Phoenix Mercury, has played in Russia for the last seven years in the winter, earning over $1 million per season — more than quadruple her WNBA salary. She last played for her Russian team UMMC Ekaterinburg on Jan. 29 before the league took a two-week break in early February for the FIBA World Cup qualifying tournaments.

More than a dozen WNBA players were playing in Russia and Ukraine this winter, including league MVP Jonquel Jones and Courtney Vandersloot and Allie Quigley of the champion Chicago Sky. The WNBA confirmed Saturday that all players besides Griner had left both countries.

The 31-year-old Griner has won two Olympic gold medals with the U.S., a WNBA championship with the Mercury and a national championship at Baylor. She is a seven-time All-Star.

"Brittney Griner has the WNBA's full support and our main priority is her swift and safe return to the United States," the league said in a statement.