Japan's external trade promotion unit is seeking a larger budget this year to help U.S. manufacturers increase their sales in Japan. But the effort is unlikely to make more than a small dent in the country's huge trade surplus with the United States.

Aimed mostly at small and medium-sized companies, the program is seeking an increase in funding for its worldwide efforts from $50 million last year to $77.1 million for the 1992 fiscal year beginning April 1, said the unit, the Japan External Trade Organization (Jetro). More than 60 percent of the budget is allocated for use in the United States.Jetro officials here estimate their program spurred approximately $100 million in U.S. exports to Japan last year. They expect larger gains this year based on initial orders placed at trade shows in Japan and by buying missions to the United States.

One of the program's stated goals is to reduce Japan's trade surplus with the United States, which reached $43.4 billion in 1991.

The backbone of Jetro's "Export To Japan" program in the United States is a group of 18 senior trade advisers assigned to offices across the country. The advisers help state governments identify U.S. companies that manufacture products with sales potential in Japan.

Their mission is to provide assistance to smaller companies who would not otherwise have the resources and experience to crack the Japanese market, said Tetsuo Matsufuji, Jetro's president.

In Detroit, Jetro's program has been warmly received.

"I think it's a good, even an almost excellent program," said Ernest Olson, manager of export business development for the Greater Detroit Chamber of Commerce.

But at the same time that Jetro is assisting some medium-sized Michigan companies to export to Japan, it has not been particularly helpful to the state's core machinery and automobile industries, Mr. Olson noted.

"It's looking at some areas Detroit is not especially strong in," he said.

Those areas include timber, log homes, and fruit preserves.

Some companies that have benefited from Jetro's program say the organization has provided the most help in making introductions to potential Japanese clients.

"They helped set-up interviews with companies who in the past would politely say 'Thank you, but no thank you,"' said Mississippi catfish farmer Gerry Holaday.

Amerlink Inc., a North Carolina builder of log homes, said Jetro helped establish links with 50 percent of its current Japanese accounts.

But Mr. Holaday also believes he received special attention from Jetro only

because his industry produces goods unavailable but in demand in Japan.

"To be honest with you, they probably expressed an interest in us because we don't directly compete with anything they produce there," he said.

That is a sentiment shared by Judge Morris, director of international trade for the National Association of Manufacturers.

"It's doubtful that we can look to Jetro or any other Japanese organization to promote U.S. exports that generally compete with leading Japanese industries," he said.

Mr. Morris's comment was less of a criticism of Jetro than it was of U.S. government efforts to increase international competitiveness and expand exports.

In Congressional testimony delivered Wednesday, NAM said it would not support a trade bill introduced by Rep. Richard Gephardt, D-Mo., partially

because it tied trade sanctions directly to targeted reductions in the U.S. trade deficit.

"Yes, we need to urge Japan and others to make changes, but we are not going to make Japan less competitive. We must become more competitive ourselves," the NAM said in its testimony.