Japan has no plans for a major increase in automobile production, its trade officials said yesterday, in a message meant to defuse the growing demands in the U.S. for restrictions on imports of Japanese cars and trucks.

President Carter is to interrupt a trip to Japan today to meet with U.S. auto industry leaders in Detroit, to announce the administration's plan for helping the industry through its current economic calamity. He will continue to Japan, to attend a memorial service for Japanese Prime Minister Masayoshi Ohira, who died June 12.

The statement yesterday by Japan's Ministry of International Trade and Industry denied that Japan was planning a further expansion of its vehicle production capability, to feed a new export campaign. Japan now accounts for 22 percent of the cars and trucks sold in the U.S., its share having doubled in three years.

A Carter administration official called the statement reassuring, but added, "we're a long way from being out of the woods."

Japan outpaced the United States in auto production by more than one million vehicles during the first half of 1980, according to industry officials in Tokyo, and most of the growth in Japanese production is exported abroad.

The details of the president's announcement were still being worked on last night and administration officials were not certain how Carter would deal with the sensitive trade issue, which has sharply divided his advisers.

Those who see the survival of Chrysler Corp. and Ford Motor Co. threatened by Japanese imports have reportedly advised the president to call for an accelerated review of a major pending trade complaint against Japan.

A petition by the United Auto Workers to the International Trade Commission, calls for quotas and higher tariffs on Japanese auto imports if Japan is not willing to increase investments in auto manufacturing plants in this country. The ITC, a U.S. government agency, normally would not reach a decision until late November -- after election day. If the case is accelerated, however, that decision could come in August or September, at the outset of the campaign.

Other advisers, however, have reportedly urged Carter not to intervene in the trade case because of the damage that might be done to overall U.S. trade objectives by such a move toward trade protectionism.

Treasury Secretary G. William Miller would say only that the announcements today by the president will be a first slice in a long-term response to the U.S. auto industry's plight. "The problem is not going to be solved in six months. We can't wave a wand," Miller said in an interview. b

An increase in Small Business Administration loan funds available for hard-hit automobile dealers is one short-range measure that may be announced, officials said.

The National Automobile Dealers Association estimates that nearly 750 of its 28,000 members have gone out of business in the past six months because of the collapse of large car sales and heavy interest rate burdens. This predicament has begun to ease, although many dealers are still in serious financial trouble, NADA says.

The president is expected to announce formation of a top-level industry-union-government committee to plan longer-range policy changes to help the industry recover, administration sources said. Changes in antitrust law that would permit auto company cooperation on environmental and safety research, and government support for new technology are two areas a tripartite commission could deal with, officials said.

Without such a joint strategy, the pressure for Congressional restrictions on Japanese auto imports next year could be unstoppable, administration sources say.