DETROIT — The global shortage of semiconductors is forcing General Motors and Ford to further cut production at North American factories as chip supplies seem to be growing tighter.

The shutdowns likely will crimp dealer inventory of vehicles made at the plants.

Semiconductors are used in the infotainment, power steering and braking systems, among other functions of a vehicle.

The shortage began in 2020 as multiple vehicle plants shut down early in the coronavirus pandemic, and chip suppliers directed them to other industries. Now that vehicle manufacturing and purchasing has bounced back, there is a shortage of available chips.

GM says it has managed to keep factories humming that make hot-selling and profitable full-size pickup trucks and SUVs.

The chip shortage has already been rippling through markets since last summer, but it has hit the global auto industry hardest.

The production cuts and plants closures range from a week or two to several weeks. Some of the plants have already been sitting idle because of the chip shortage.

GM says Thursday that production cuts will take place at its Spring Hill, Tennessee; Ramos Arizpe, Mexico; Ingersoll, Ontario; Fairfax, Kansas; Lansing, Michigan, Delta Township; and Lansing, Michigan, Grand River factories.

Ford's plans include adding more downtime for two plants in Illinois and Missouri and a temporary closure at its Flat Rock Assembly plant in Michigan.

Impacted vehicles include the Ford Explorer, Lincoln Aviator, Ford Mustang, Transit van, GMC Acadia, Cadillac XT5, and Buick Enclave.