The Japanese government yesterday asked its auto industry to reduce car exports to the United States, voluntarily by 7 percent this year, according to press reports from Tokyo -- a cutback of 120,000 vehicles that apparently stops well short of what Congress and the U.S. auto industry have been seeking.

As Japanese trade officials began a series of conferences with that country's auto producers, Commerce Secretary Malcolm Baldrige said here that Japan is waiting for more evidence of sacrifice by American auto makers and the United Auto Workers union to help the U.S. industry recover.

"If there aren't statements forthcoming, right now I wouldn't predict what the Japanese government would do," Baldrige told reporters yesterday.

"The Japanese government and industry might decide to make a token effort, which in turn might be interpreted that way" on Capitol Hill, he said. Such an effort, he said, probably would lead to legislated import quotas from Congress -- an outcome the Reagan administration deeply hopes to avoid.

Administration officials were unsure whether the voluntary limit cited in Japanese press reports yesterday was a firm proposal by the Japanese government or another move in the convolute aujto trade dealings between the two countries.

"We're trying to make them move and they are floating things," said one U.S. official.

Two Japanese news services reported that the Ministry of International Trade and Industry had asked Japanese auto makers to hold exports to the United States to 1.7 million units, this year and next, compared with the 1.82 million shipped in 1980.

It wasn't clear whether the 1.7 million figure includes shipments of Japanese-made vans. A bill to limit car shipments to 1.6 million units is gaining support in the Senate and the two sides could be close to agreement if the Japanese accept that figure and add 100,000 vans to the total, administration officials said. Ford Motor Co. has asked for a limit of at least 1.2 million cars.

The Japanese government's proposal was reportedly made in separate meetings with executives of Mitsubishi Motors Corp., Honda Motor Co., and Fuji Heavy Industries, the maker of Subaru cars, according to the Nihon Kezai Shimbun, the leading Japanese economic journal.

The journal and the Kyodo News Service, citing government sources, reported that the companies did not accept the proposal. The reports were not confirmed.

Japanese government officials will meet later this week with the major auto manufacturers -- Toyota Motor, Nissan Motor, Isuzu Motors and Honda Motor -- in hopes of concluding a voluntary export policy by the weekend. If the effort succeeds, a trade delegation would come to Washington immediately to brief U.S. officials, the Japanese press reported.

Baldrige appeared yesterday to be inviting the American auto makers to take further steps to molify their Japanese competitors, while warning Japan that it continues to risk trade sanctions by Congress if a satisfactory import limit isn't set soon.

"The balance, I think, is very delicate," he said.

Because of the hands-off policy that the Reagan administration is officially committed to, Baldrige would not indicated what an acceptable import number would be, nor would he suggest concessions that the American companies and the UAW might make to move the auto dispute further toward resolution.

"The Japanese government, we feel, sincerely wants to work out a voluntary restraint program. However, the Japanese government cannot do this unless they have a concensus in Japan," he told reporters at a breakfast briefing.

Japanese auto companies complain that they are asked to bear the full burden of helping the U.S. industry recover, Baldrige said, and want more detail about what the American auto makers can do to "pick themselves off the ground."

The problem is that the American companies believe they've sacrificed enough already, and UAW leaders cannot make wage concessions in advance of the local elections scheduled for May and June, he said.

A Commerce Department analysis indicates that the American auto makers could face a $12 billion shortfall in raising the $80 billion needed to complete a five-year modernization program they have undertaken to catch up with Japan, Baldrige said.

Ford Motor Co. Chairman Philip Caldwell is expected to respond to Baldrige's request today, but no new concessions are foreseen.

Both the U.S. and Japanese governments hope to conclude an understanding before Prime Minister Zenko Suzuki's meeting with President Reagan here May 7-8. But Robert Hormats, assistant secretary-designate of the State Department, told a Senate committee yesterday that such an agreement is "a possibility, not a probability, now."