COLUMBUS, OHIO, SEPT. 17 -- Honda Motor Co. said today it plans to export up to 70,000 cars made in the United States to Japan and other countries by 1991 and increase the amount of U.S.-built parts in its vehicles to 75 percent, also by 1991.

The company announced a $561 million expansion of its U.S. manufacturing operations, including the construction of a second auto assembly plant near Marysville, Ohio.

Beginning next year, Honda will begin exporting to Japan motorcycles and cars made in Ohio, said Tetsuo Chino, president of Honda North America.

"In 1988, an initial program will consist of 500 motorcycles and 3,000 automobiles. In 1991, we intend to export 70,000 cars per year from Ohio to Japan and other countries," he said.

Also by 1991, the car maker said, 75 percent of the parts in the cars produced at Marysville would be made in the United States, compared with 60 percent for 1988 models.

Honda, the nation's fourth-largest auto maker, also said it would expand its research and development facilities. "There are approximately 180 associates employed by Honda R&D in the United States," Chino said. "By 1991, we will expand that number to 500."

Construction of the $380 million auto plant is expected to begin in February 1988 on what is now the site of the state's transportation research center. Production on what will be the company's third assembly line is to begin in August 1989. The plant would have a capacity of 150,000 cars annually and would employ 1,800 workers.

The new plant is expected to produce Honda's four-door Civic model, although it would be capable of producing virtually any of the company's cars.

Honda also will spend $150 million to expand its engine plant in Anna, Ohio, to increase engine production to 500,000 engines a year, and hire an additional 500 employes. That is in addition to a $450 million expansion announced in January to produce engines and drive-train components for the cars manufactured at Marysville.

The company already employs 4,000 people at its Marysville plants, who produce 320,000 cars and 60,000 motorcycles each year.