"There are certain factors in the American labor environment that are unsettling, to say the least," said Masataka Okuma, executive vice president of Nissan Motor Co. Ltd. Speaking to about 500 individuals at an automotive "world congress" here sponsored by the trade newspaper Automotive News, Okuma cited labor problems as his third reservation about establishing a manufacutring plant in the United States.

The first is the handicap of "extremely-small-scale production . . . Second, after American automakers have retooled their plants and begin to turn out small cars with a vengeance, there is a strong possibility that at some point the market will become glutted with small models," he said.

At a press conference following his talk, the high-ranking and uncommonly candid Japanese executive said "certain elements in the labor environment" make him uneasy. "I don't mean to blame the UAW's labor customs and so forth . . . But there is a labor difference in Japan and the U.S.," Okuma said.

Nissan, which manufactures Datsun cars and trucks, has authorized an initial commitment of $60 million to establish a head office in Delaware for the assembly of Datsun trucks in the United States. Okuma said, however, that New Jersey has been ruled out as a location for the plant -- meaning the company will not buy the Ford Motor Co. Mawah assembly plant there, which was closed a month ago.

Three locations are un der consideration now, and a final decision will be made within a month, he said. Okuma hinted that the locations preferred are in the Southeast.

"Probably we will be able to introduce some Japanese labor customs in the U.S.," he said. Okuma's talk, which was billed by Datsun's U.S. people as "extending an olive branch" also included these statements:

Japanese autoworkers are educated as well or better than their counterparts in other countries, and as well-paid as U.S. autoworkers.

There is "bitter competition" among the various Japanese automakers.

A potential glut in small cars which occurs when U.S. makers are completely tooled up could be pushed by additional exports from developing nations such as Brazil, Mexico, Korea and Taiwan, he said. Also, socialist nations such as Russia, Poland and China probably will begin to export, he said. Okuma termed that last as "only a matter of time" and "a potential threat to us."

Sales of Japanese-made cars in the United States have been falling each month since March, and their market share "peaked in May and has been falling since," he said. The rise in the value of the yen will force price increases of Japanese vehicles and thus make those imports "maintain a moderate level" he said.

Japanese car makers are "frightened" by the scale of resources U.S. manufacturers have, and "the specter" of 1 million single-model world world cars being a result of the U.S. industry's $80 billion retooling $80 billion retooling program.

Recent changes in liberalization of trade and investment in Japan have made that country the first "in the world to abolish all import duties on fully assembled automobiles," Okuma said.