Japanese leaders are considering curbs on exports to ease their country's simmering trade tensions with the United States and other countries.

By contrast, in past months the government has focused on relaxing import barriers as the preferred method of reducing its burgeoning trade surpluses, which totaled $37 billion with the United States alone last year.

Proposed methods for keeping the lid on exports range from self-restraint by companies to imposition by the Japanese government of a special surcharge on exports.

Prime Minister Yasuhiro Nakasone, speaking to a meeting of cabinet members and ruling party leaders today, said the country must be prepared to control exports to head off pressure for the more extreme step of an export surcharge.

Nakasone spoke of a need to prepare "step-by-step measures" to curb exports, according to a senior Japanese economic planning official who attended the hour-long meeting. It had been called to discuss a package of market-opening measures the government has promised to announce next month.

So far, new export restraints are primarily just talk. Any calculated reduction of exports would be a traumatic decision for Japan, which has built much of its postwar prosperity on foreign sales. Many analysts here see the surcharge as only a distant possibility.

But at the same time, many Japanese leaders believe pressure from the U.S. Congress, where the anti-Japanese furor of March and April has cooled, is likely to grow again later this year.

Despite market-opening efforts here, the U.S. deficit with Japan is continuing to widen. According to Jiji Press news agency, U.S. Commerce Department figures show the deficit rose by about 50 percent in the first four months of this year compared with last year, from $10.4 billion to $15.1 billion.

The Japanese government for years has promoted "orderly marketing" by its companies abroad. It has applied limits (usually in response to protectionist rumblings in market countries) to a variety of export lines, notably automobiles.

Japan's decision in March to raise the U.S. auto export quota from 1.85 million vehicles to 2.3 million per year was depicted here as a generous act of restraint at a time when Japanese surveys showed a demand for about 2.7 million vehicles. It was condemned in Congress, however, as an effort to flood the U.S. market.

In past weeks some leaders of the ruling Liberal Democratic Party have told business leaders the country must consider a broader-brush approach to exports, in the form of a surcharge. By making Japanese goods more costly to foreign buyers, a surcharge would tend to reduce shipments abroad.

Opponents in the party and government bureaucracy say a surcharge would run counter to the principle of fair trade, unjustly penalize Japanese companies, and perhaps backfire by creating a stampede of exports just before going into effect.

But supporters contend those scenarios are preferable to having the United States impose an import surcharge on Japanese goods, as a number of bills now before Congress propose. By acting first, Japan would be able to determine the surcharge level and collect the revenue for itself.

At today's meeting, officials also discussed new measures to encourage imports into Japan, where many foreign goods still face a maze of cultural and bureaucratic obstacles.

The July package will include cuts in import tariffs. However, a debate is in progress here over whether they should be unilateral or should be implemented only if Japan's trading partners agree to do the same.

The Ministry of International Trade and Industry and other government agencies are reported to favor reciprocal cuts. But Nakasone, speaking at today's meeting, reportedly said that hostility toward Japan is so strong abroad that radical, unilateral steps are needed to show that Japan means business. "What is important is that Japan must act by itself and lead the way," Nakasone reportedly told the meeting.

Officials here also say that the government will announce reforms of import procedures, government procurement rules and standards that foreign products must meet to be sold in Japan. All are seen by foreign businessmen as import barriers.

In addition, to cut the deficit the government is considering a one-time purchase of passenger aircraft to be used by the prime minister and senior government leaders for trips abroad.