The nation's two largest automakers yesterday disclosed that they had significantly cut their production plans for the final months of the year.

General Motors Corp. announced that it would produce 300,000 fewer cars in the final three months than it had originally planned -- a 22 percent reduction. Some of that cutback had been previously announced.

And Ford Motor Co. said, in response to questions, that it also was trimming its fourth-quarter production schedule. The company said it will build 425,000 cars, 7 percent fewer than it built in the same quarter a year ago, and that it will assemble 342,000 trucks, 8 percent less than last year.

Production cutbacks at GM, Ford and Chrysler Corp. this week found 14 assembly plants shut down across the country with 38,000 workers laid off. Many of the layoffs are temporary, but they have cast a pall over an industry already struggling with declining sales and profit margins. They have also begun to drag down the economies of Midwestern states that had resisted the economic downturn engulfing much of the Northeast.

Workers on temporary layoffs normally collect 90 percent of their usual take-home pay through a combination of public unemployment benefits and company-funded layoff protection plans negotiated by the United Auto Workers.

GM Chairman Robert C. Stempel, speaking to employees at GM's truck plant in Fort Wayne, Ind., last night, blamed the Persian Gulf crisis for declining auto sales. Consumers worried about the possibility of military conflict are staying out of showrooms, he said.

GM has been rewriting its production schedule almost continuously since Iraq's invasion of Kuwait in August, as gasoline prices soared and consumer confidence sank. The company initially planned to build 1.36 million cars and trucks in North America during the last three months of 1990, but later decided to slice 181,000 vehicles from that schedule.

Now, said Stempel, with consumer confidence at its lowest since the 1980-82 recession, GM will cut an additional 111,000 units from its fourth-quarter plans, rather than build vehicles that could wind up sitting indefinitely on storage lots.

"We are determined to keep our inventories in line with demand," Stempel said. It was unusually frank talk from the executive of a company that traditionally has said little about production plans, particularly if those plans spelled bad news. Stempel's aim, some GM officials said, was to signal stockholders that the company recognizes it is moving through troubled times and that it is willing to make the necessary sacrifices to stay on track.

"To sit down and pretend that things are great and wonderful would be irresponsible," said GM spokesman Terrence P. Sullivan. "We're not saying that the world is coming to an end. In fact, we're optimistic about the long term. But there are some negative trends out there that have to be noted."

The cuts, combined with an apparent consumer shift to less-expensive vehicles, also means that GM's fourth-quarter earnings "will decline significantly relative to our recently released third-quarter results," Stempel said, because of the lower production, the cost of rebates needed to sell cars, costs of GM's new labor agreement and the fact that people are buying smaller vehicles on which GM makes a smaller profit.

GM's stock closed yesterday at $37.50, down 25 cents.