Ford Motor Co. said today that it is exploring a possible joint venture with Toyota Motor Co. to produce Japanese vehicles in Ford assembly plants.

Ford President Donald E. Petersen, responding to press reports from Japan, confirmed that Toyota's executives proposed the idea last month during Petersen's visit to Japan.

If a satisfactory agreement could be worked out, "I would welcome such a result," said Petersen. "There is no truth to the reports that we have reached an agreement with Toyota." It is far too early to predict whether a satisfactory venture can be arranged, he said.

The Ford-Toyota discussions were disclosed by the Japanese press, quoting unnamed Toyota executives as saying that a basic agreement had been reached to produce 240,000 Toyota cars in a remodeled Ford plant with the two companies splitting the investment.

Toyota, Japan's largest auto manufacturer, has been under pressure from the Japanese government to establish a manufacturing plant in the United States to reduce the volume of auto impots by the United States from Japan. s

The Carter administration and the United Auto Workers also have called on Japan to tell Japanese automakers to invest here. President Carter announced in Detroit Tuesday that the administration would ask for rapid consideration of a UAW complaint agaist Japan pending before the International Trade Commission. The UAW claims Japanese imports have seriously injured U.S. producers and wants tough limits on such imports unless Japan's producers begin manufacturing here.

Currently, Honda Motor Co. is the only Japanese auto firm that has announced plans to assemble autos in the United States. Honda says it will build a new plant in Marysville, Ohio, next to its existing motorcycle plant, with production starting by the end of 1982. It plans to produce at least 120,000 cars a year.

Nissan Motor Company, which manufactures Datsun cars and trucks, says it will establish a light truck plant, either in the Great Lakes region or the southeastern United States.

A Nissan official recently toured Ford's Mahwah, N.J., plant which was closed last month, but the Japanese company has not expressed interest in the facility. The Mahwah plant, one of Ford's largest and most modern, and a Los Angeles plant closed in January are possible sites for a joint venture with Toyota if such a venture comes about.

The Ford-Toyota discussions also include Toyo Kogyo Company, manufacturers of Mazda cars and trucks and one of Ford's major suppliers. Ford owns 25 percent of the company.

Congressional analysts have noted that Toyota and Nissan would have more difficulty establishing a U.S. plant because, unlike Volkswagen and Honda, the two large Japanese firms build many different models. By concentrating production on single models, Volkswagen and Honda can achieve the sales volume necessary to justify a production plant, the analysts said.

Nissan said this year that a production plan would cost up to $400 million, an investment that made little sense under current conditions.

Toyota, however, has hired two U.S. research firms, A.D. Little Co. and SRI, to study the possible manufacturing venture in the United States. The report is due to be completed this year.

In addition to the political pressures on the Japanese firms, their interest in U.S. manufacturing undoubtedly was increased by a sharp rise in the effective tariff on Japanese light truck imports.