General Motors Corp. and Toyota Motor Corp., two of the world's largest automakers, have agreed to joint production of a car in the United States, industry officials confirmed last night.

The officials, both in the U.S. and Japanese auto industries, said the agreement probably will be announced Monday.

"We are not denying that there is an agreement. We are saying that there has not yet been a formal announcement, either by Toyota or General Motors," a Japanese auto industry official said.

"You're okay in saying that there is something. They've had about 90 percent of it done for some time, now. It wouldn't be incorrect to say that they are there," said a U.S. industry official.

Some details of the agreement were reported yesterday in Japan's Kyodo News Service. According to the report, also based on unnamed industry sources, the 10-year agreement would:

* Establish an equally owned company to produce an annual rate of 200,000 small, front-wheel-drive cars at GM's idle plant in Fremont, Calif., beginning in late 1984;

* Provide $300 million in initial capital for the joint venture;

* Allow 50 percent U.S. content to be used in the cars, which would be designed to replace GM's aging, rear-wheel-drive Chevrolet Chevette and a similarly designed Pontiac model.

Neither GM, the largest U.S. automaker, nor Toyota, the largest automaker in Japan, would comment on the specifics in the report. But sources pointed out that the two companies have been trying for nearly a year to come up with a pact that would benefit Toyota by undercutting rising protectionist sentiment in the United States, and would help feed GM's hunger for a new fleet of small, front-wheel-drive cars.

GM has argued that it was being driven out of the small-car market because the Japanese could produce small cars for $1,500 to $1,700 less per vehicle than the cost of making similar vehicles domestically. GM said in the past that any decision to produce cars with Toyota would be temporary--kept in place long enough to give GM a chance to come out with its own competitive products.

As an example of their temporary joint-production strategy, GM officials point to their experience with Isuzu in the production of Chevy LUV (light utility vehicle) trucks. GM had sold 593,100 of the LUV trucks between September 1972 and September 1982. But GM began phasing out the LUVs last year when it introduced its own Chevrolet S-10 light trucks.

Still, GM retains a 34 1/2 percent equity interest in Isuzu, which also is expected to produce about 150,000 Isuzu STs (sports touring) passenger cars for GM for sale in the 1984-model year. GM also anticipates purchase of 200,000 front-wheel-drive Suzuki minicars for 1984 sales. Those agreements, combined with the Toyota deal, would give GM an annual supply of nearly 500,000 small cars to take to market.

That development worries domestic competitors such as Ford Motor Co. and Chrysler Corp., which have been scrambling to come up with products to compete in the small-car wars.