Japan, seeking to blunt criticism of its trade practices when Prime Minister Yasuhiro Nakasone and two of his cabinet ministers make trips abroad this month, today announced plans for reforms of government rules that foreign companies say impede their sales in Japan.

The measures, approved today at a meeting of cabinet members and leaders of the ruling Liberal Democratic Party, were presented as goals and principles rather than in specific form. Many will require acts of the Diet, or parliament, which appears to be assured.

U.S. trade experts here expressed hope the measures would improve market access. Herbert F. Hayde, president of the American Chamber of Commerce in Japan, called it "a good set of objectives," but said "I'm really going to look to see what the details are going to be."

Many Japanese officials, contending their country already is an essentially free market, say that such measures can have only a superficial effect on Japan's trade surpluses.

The announcement was timed to smooth the way for a visit to France, Italy and Belgium that Nakasone will begin later this week, according to Makoto Kuroda, chief of the foreign trade policy bureau of the Ministry of International Trade and Industry.

The announcement also is keyed to foreign tours by MITI Minister Keijiro Murata and Foreign Minister Shintaro Abe. Murata has departed on a tour to France, Canada and the United States, and Abe leaves Wednesday for Malaysia to attend a meeting of foreign ministers of member states of the Association of Southeast Asian Nations and their allies.

Japan is under mounting pressure from trading partners around the world to rein in its surpluses and open its markets further. Last year's surplus with the United States alone came to $37 billion.

The imbalances are continuing to grow, however. Figures released today by the Ministry of Finance showed a record surplus in Japan's overall trade accounts of $17.7 billion in the first half of this year compared with $13.5 billion in the same period last year.

Today's measures are meant to give added form to an "action program" that Nakasone promised to devise last April. In June, his government announced its intention to cut tariffs on more than 1,800 product categories as part of that program.

The rush to get out the statement today meant that many key elements were left indistinct. But officials promised more details at the end of this month.

Many of today's measures touch on technical standards that products must meet to be sold here. Foreign companies complain that Japan's system is too strict and time-consuming and tends to discourage introduction of their goods. They also chafe under rules that in many cases require testing already done in their home countries to be repeated in Japan.

Today, the government pledged to reduce the number of items that are covered by various certification systems and to simplify standards that are to remain in place.

The revisions also would allow producers to "self-certify" more items, rather than having to submit them to government inspection.

Attempts would be made to cut by 50 percent the number of licenses that producers of cosmetics such as liquid hair dressings will have to obtain, the government said. In addition, the government pledged to accept foreign test data "to the extent possible," assure that opinions of foreign companies are heard in drafting standards, and adjust Japanese standards to meet international ones in such areas as safety for electrical appliances.

Today's measures also promised to reform procurement by Japanese government agencies. Foreign companies long have complained that their Japanese competitors have an inside track in getting this business.

Bidding will be made more open and procedures will be standardized, the government said.