Prime Minister Yasuhiro Nakasone, citing "dangerous times" for Japan in world trade, tonight made public a market-opening package that contains broad promises for liberalization and tariff reductions but few specific new steps to be taken immediately.

Nakasone said Japan will devise an "action program," to be carried out during the next three years, to open its market further to foreign goods and reduce a burgeoning trade surplus with the United States. It will be ready in outline form by July, he said.

Nakasone made his announcement in a highly unusual television address to the nation. Using colored charts and a pointer, he told viewers that Japan's surplus is creating enmity overseas. "I call on you, the Japanese people, to buy as many imported goods as possible," he said.

[The Reagan administration applauded Nakasone's efforts to expand U.S. imports but said more needs to be done. Critics said Nakasone's initiative was inadequate and would not stem the growing protectionist sentiment in the United States.]

Bills now before Congress to keep Japanese exports out of the United States, if enacted, could cause "a serious depression in Japan," Nakasone said. "Many people would be unemployed. Japan is now facing such dangerous times."

Japanese officials depicted his speech as marking the start of a shift away from the export-oriented strategy that helped to build Japan's postwar prosperity. The country is now moving toward a more mature economy in which imports will come closer to balancing exports, they said.

It remained unclear what role the government would play in any shift toward imports. Officials here said it planned only publicity and moral suasion to speed the changeover. Market forces would be the main impetus, they said.

The government had been working on tonight's measures since shortly after Nakasone met President Reagan in Los Angeles in January. The two leaders agreed then to concentrate on further opening Japan's market in four specific sectors: telecommunications, electronics, forestry products and pharmaceuticals and medical equipment.

In recent weeks, Nakasone repeatedly reminded visiting Americans that tonight's announcement was coming, apparently as evidence of Japan's good faith in trying to reduce growing trade tension with the United States, which recorded a $37-billion deficit with Japan last year.

Some senior officials in the Japanese bureaucracy, however, worried that Japan was raising expectations that the package announced tonight would not satisfy. This is Japan's seventh market-opening package since December 1981.

Officials said previous packages were composed of ad hoc measures. This one, they said, is composed of elements too deep-reaching to be implemented overnight. "We cannot expect anything dramatic," said a senior official at the Ministry of International Trade and Industry.

Nakasone's plans still would face an uphill battle through Japan's powerful government bureaucracy and through the Liberal Democratic Party, which does not appear to be completely united behind them.

Japanese prime ministers rarely have taken their cases directly to the public. Nakasone's use of television reflects his more assertive leadership style and, apparently, a desire to show the United States that he means business.

In his address, Nakasone chided U.S. businessmen for not trying hard enough to sell in Japan. "All Japanese businessmen in America speak English. But no American businessmen in Japan speak Japanese, do they?" he said he had told a U.S. official.

However, he said, Japan still needs to change. "The important thing is that all foreign countries have an equal chance to export," he said.

Many of his promises tonight were drawn from a report released today by a 10-member study commission chaired by former foreign minister Saburo Okita. The group was appointed by Nakasone to offer guidance on Japan's changing role in the world economy.

The report concluded that the United States bears most of the blame for its deficit with Japan, a view shared by many in the U.S. government. It cited economic recovery in the United States and the dollar's high value as the prime factors behind a wave of imports into the United States in 1984.

"Japan's trade is not determined by Japan's policy alone," Okita said at a press conference tonight.

"Freedom in principle and restrictions as exceptions" should be the government's guiding policy, the report said. Japan should offer to eliminate all tariffs on manufactured goods in concert with other industrialized nations and continue to work toward a new round of multilateral trade talks.

Market access in Japan also could be improved through initiatives in such areas as import regulations, technical standards, certification, government procurement, financial and capital markets and services, it said.

The report recommended that the government pay more attention to fostering domestic demand, which would result in more imports and less pressure to export. It said this could be done through deregulation of business, upgrading of public facilities, shorter working hours and tax reform.

This is a controversial issue in Japan because economic policy has traditionally served to keep demand low. Since the end of World War II, the government has been more concerned with promoting investment and saving than consumption.

Nakasone endorsed the report's objectives tonight and promised action to implement them. The goal will be to "leave the options as well as the responsibilities to consumers," he said in a written statement.

Nakasone listed other steps or goals in the package, among them:

* Financial aid will be channeled to Japan's ailing forest products industry. After that starts, "the government intends to positively consider reduction of tariffs on plywood, etc. . . .," a government paper said, "with a view to starting implementation approximately from the third year."

* Decisions on other unspecified tariff reductions will be made by the end of June. Many of these are believed to apply to products from Southeast Asia. Any tariff cuts would have to wait until April 1, 1986, to be implemented, as they must be approved by the Diet, or national legislature.

* Japan has agreed to accept foreign test data for certain medical equipment and pharmaceuticals. However, pharmaceuticals to which this will apply will be limited to those used outside the body in diagnosing rather than treating illnesses. Foreign applicants will be given more access to decision-makers.

* Nine-and-one-half-foot-high cargo containers that U.S. companies want to use on Japanese roads will be cleared for use "under certain conditions."

* The government will work to encourage imports of manufactured goods. Measures will include lower-cost financing, requests to businesses to increase purchases abroad, public advertising campaigns and the holding of import fairs. Many of these steps built on previous government plans, though officials say they will be given new strength.

* As of April 1, the Export-Import Bank of Japan has been authorized to finance the purchase of foreign satellites. The government will move quickly to solve questions on radio frequency allocation, which are currently an obstacle to satellite purchases.

* The government will work to get a settlement "as early as possible" to foreign lawyers' long-standing fight for the right to practice in Japan.