Japanese government officials say they don't expect any significant improvement soon in the large trade imbalance that has triggered American threats of punitive action against Japanese exports to the United States.

In a series of interviews, government officials admit that the "action program" promised by Prime Minister Yasuhiro Nakasone, scheduled to be announced early next month, is not likely to satisfy critics in Congress who are disturbed by a $36 billion trade deficit with Japan last year that is likely to widen to $45 billion to $50 billion this year.

Japanese officials say that only a fundamental shift in macroeconomic policies by the United States and Japan, designed to bring down the value of the dollar against the yen, can reduce Japan's trade surplus in the long run.

Elder statesman Saburo Okita, recognized as the architect of the Japanese economic "miracle" of the 1960s, said in an interview that "if Americans and Europeans expect quick results out of the action program, they will be disappointed."

The search for solutions to the problem has been so desperate that the Japanese government reportedly has asked the Keidanren (the Japanese equivalent of the National Association of Manufacturers) and other major business groups to comment on a proposal for an export surcharge.

American officials here are not enthusiastic about that idea, much preferring to see the Japanese deficit reduced by greater imports into this country. Historically, however, Japan has always been more willing to place "restraint" on exports than to allow a wider wedge of imports into its economy.

Okita acknowledged that anti-Japanese rhetoric and actions have mounted. He cited in particular the public statement of a longtime friend of Japan, Hewlett-Packard Chairman David Packard, that the United States now must consider imposing quotas on nonconsumer electronic goods from Japan.

"To a certain degree, this pressure may be useful," Okita said. "To a certain extent, it could be to our benefit; basically, we should welcome a policy to open up our markets."

But for the public here or in the United States to see much change in the huge trade imbalance, Okita said, more fundamental changes will be necessary. On the Japanese side, that would require a substantial expansion of the domestic economy to encourage consumption and housing construction. But because of Japanese fears that this would stimulate inflation, the Nakasone government resists such a course.

On the American side, it would require dramatic reductions in the huge budget deficits -- well beyond the deficit reduction bills being considered by Congress -- to lower the dollar premium over the yen.

In the face of this dilemma, officials of the Reagan administration, negotiating here with their counterparts in the Japanese bureaucracy, express great frustration.

Deputy U.S. Trade Representative Michael Smith, leading a team of at least 10 American negotiators, said that little new had been accomplished in persuading Japan to drop what the American side insists are impediments to free trade in telecommunications, forest products, medical and health equipment and other special products.

Smith told reporters that the complaint filed with his office by the Semiconductor Industry Association against Japanese chip makers is an example of what American industry representatives consider "unfair trade practices." The industry charges that Japanese barriers prevent the growth of American sales in Japan and that at least one major Japanese exporter, Hitachi Ltd., is dumping computer chips in the United States.

At the same time, Japanese government officials see no solution to the broader trade problem and confess that the prospects for damage to the overall U.S.-Japanese relationship are frightening.

In his office at the National Diet Building, Kiichi Miyazawa, chairman of the ruling Liberal Democratic Party's executive council, said: "We are in deep water this time, and we do not know how to extricate ourselves; we don't know how to go about it."

Although Nakasone, in earlier meetings with President Reagan, committed himself and his government to take steps to boost "access" to the Japanese market, the sprawling Japanese bureaucracy is bitterly divided on whether and how to take steps to boost Japanese imports.

One group, including officials at the ministry of foreign affairs, is earnestly trying to reduce barriers to imports, convinced that new antagonisms in Congress are certain to yield virulent protectionism in the form of import surcharges, or legislation calling for specific reciprocity treatment.

Democratic presidential hopeful Rep. Richard Gephardt of Missouri reportedly is considering legislation that would require Japan to reduce its trade deficit with the United States by 10 percent a year. Stiff reprisals also are being shaped by other Democrats, a trend that some Reagan officials concede may drive the administration to back away from its currently softer stance.

But another group of officials in various Japanese ministries advises taking the minimum steps necessary, in the belief that the storm will blow over as it has in the past after small concessions have been made by Japan.

"We have to try to buy time," said one official in a key ministry, "and hope that perhaps the dollar will come down, and that the slowdown in your economy will dampen the enthusiasm for importing goods."

But not all trade experts here are convinced that there are new pressures. Exemplifying the view that the present crisis is but one more stage of an ongoing process, Professor Yoshinobu Yamamoto of Saitama University said, "I think the trade issue is a recurrent event; nothing much has changed."

On the other hand, a senior foreign ministry official said in an interview: "We know that the Reagan administration is trying to hold back the protectionist pressures, and we're ready and willing to help them. So we hope that the action program will be meaningful and credible, not only to Americans, but to the Europeans and other Asians."

The problem, however, is that nothing can be done in the short run to prevent the Japanese surplus from rising. For the last two months, even the "invisibles" account, which used to show a deficit, has added to the Japanese embarrassment by turning into a surplus. Thus, the total Japanese "current account" shows a huge global surplus, in vivid contrast to the American current account deficit of more than $100 billion, which is turning the U.S. into a debtor nation.

According to several estimates circulating among Japanese officials, the Japanese current account surplus could soar to an incredible $500 billion a year by 1990, far above the total accumulated by the 15 nations of the OPEC cartel at the peak of their power.