The chairman of the Board of Nissan Motor Co., Ltd., a leading Japanese manufacturer, said here yesterday that the timing is not right for his company to establish auto production facilities in the United States.

Katsuji Kawamata told reporters, nonetheless, that the question of manufacturing. Nissan's popular Datsun cars in the United States "is always on our minds." Datsun and other small foreign imports have enjoyed a sharply rising demand here recently, in response to gasoline price increases and supply shortages.

Kawamata indicated that there were many market uncertainties at the moment that have postponed a decision to produce Japanese cars here, despite the warm welcome Japanese companies would get from many different states.

He mentioned as a major consideration that to produce autos "we need an economy of scale." The implication was that with American companies going heavily into the production of lighter-weight cars, the competition might be tough. "The question is," Kawatama said, "whether we could achieve mass production. That is our greatest concern at the moment."

Even as things stand, he predicted that the extraordinarily current heavy sales trend of Japanese cars here would be fading. Toyotas (the No. 1 import), Datsuns, Hondas and other Japanese cars have been hot sales items since early this year. Over-all, imports last month took 22 per cent of the American market.

Other factors that make his own company hesitate to build cars here, Kawamata said, include the serious potential impact on employment in Japan, the uncertain oil price-supply equation, and the Japanese Government effort to keep the yen at a strong enough level to assure a continued decline in the Japanese trade surplus.