Japan and the United States should work together to encourage economic prosperity and political stability in the developing world, particularly in the emerging Asian nations, the former prime minister of Japan said.

Yasuhiro Nakasone urged the two economic giants to help emerging economies diversify beyond primary products.Closely coordinated efforts between Japan and the United States are indispensable, he told a Friday night meeting of the Asia Society in San Francisco.

Mr. Nakasone praised the bootstrap efforts of China, the members of the Association of Southeast Asian nations, and the newly industrialized countries of Asia.

Nowhere else on Earth has there been such economic dynamism sustained over such a long period of time, he said. The East Asia and Pacific region is indeed alive and stirring with energy.

But he added that further progress in Asia as the world moves into the 21st century will depend on healthy relations between Japan and the United States.

Mr. Nakasone outlined a series of guidelines under a program he termed the Pacific Initiative.

He called for Japan and the United States to keep in mind their long-term objectives when dealing with bilateral trade issues. Even relatively minor actions by the two nations can have a major influence on developing countries, he said.

The statesman also urged Japan and the United States to avoid exclusivity and to seek Western Europe's aid and participation in global and regional international affairs.

In addition, Japan and the United States should remain vigilant against instability in the Asian region, he said.

Mr. Nakasone said Japan and the United States have made progress coordinating their macroeconomic policies and resolving trade problems. But further delay in resolving U.S.-Japanese economic issues could lead to a rise in protectionism which would damage developed and developing countries alike.

Mr. Nakasone said Japan must join the United States to ensure markets for Asia's newly industrialized Asian nations - Hong Kong, Taiwan, Singapore and South Korea. Although these countries have come a long way, their economies have their own difficulties and need continued support.

I do not believe it is sound to depend mostly on the United States to

absorb exports from Asian NICs in the way it has done in the past, he said, adding that Japan's exports from these nations grew 50 percent in 1987 over 1986.

The Association of Southeast Asian Nations, made up of Brunei, Indonesia, Malaysia and the Philippines, also needs support in its challenge to effect industrialization, he said.

Japan and the United States should further extend resources to support modernization in China while respecting its national character, he said.

I am convinced that the stability and development of China, combined with its increased friendship with the industrialized democracies, will be the key to stability and development in the entire Asia-Pacific region, he said.

Mr. Nakasone proposed that a forum be established, called the Pacific Forum for Economic and Cultural Cooperation, to promote the free exchange of economic and cultural information.

On the political front, Mr. Nakasone said, Japan and the United States should work to ensure that freedom and democracy in the region develop on a level with its increasing economic strength.