Mr. Trump wrote on Twitter that he wanted the Ohio plant “opened or sold to a company who will open it up fast!” He also urged G.M. to close a factory in China or Mexico instead of idling the one in Lordstown.

The president also called on the company and the U.A.W. to start talks to reopen Lordstown rather than waiting until the fall, when the two sides are scheduled to negotiate a new labor contract. G.M. and the union, however, have been in discussions since last year about Lordstown and other plants designated for closing.

“Our focus is on our members who have been impacted, and we have and will continue to leave no stone unturned to keep the G.M. plants open,” the union said in a statement.

In its November announcement, G.M. said it was also idling a car plant in Detroit, and plants in Warren, Mich., and Baltimore that make electric motors and transmissions. The action will eliminate 2,800 factory jobs. Thousands of white-collar jobs are also being cut as part of a cost-cutting drive.

G.M. recently said it would keep the Detroit plant operating until January, seven months longer than originally planned.