Tokyo — With tensions in the Middle East and uncertainty in Moscow preoccupying Washington, President Reagan is pausing to focus attention on East Asia and the Pacific.
To many observers, the President's six-day visit to Japan and South Korea seems largely a public relations exercise laden with political objectives.
But the state visit has a larger canvas as well. Mr. Reagan, say his aides, is seeking greater cooperation between the United States and Japan on global as well as bilateral issues.
With its heavy news media coverage, the visit enables Mr. Reagan to continue ''acting presidential'' and dominating the political scene at home. And it gives him an opportunity to boost the stature of Japanese Prime Minister Yasuhiro Naka-sone, who, battling for his political life, is moving toward elections later this year.
''In the 21st century, we can foresee vastly expanding economic, political, and cultural bonds with these countries,'' Mr. Reagan said in Alaska en route to Tokyo. ''I believe we will witness a wave of productive and creative endeavors improving the quality of life on both sides of the Pacific.''
On arrival in Tokyo, Mr. Reagan soon got down to the first round of talks with the prime minister on the difficult questions of trade and the dollar-yen exchange rate. These are politically sensitive topics for Mr. Nakasone.
But US administration officials indicate that the President is attuned to Japanese political realities and will not do anything to embarrass the prime minister. He will simply stress in private the importance of progress in American eyes.
''No relationship between two countries is more important than the relationship between the United States and Japan,'' the President told his hosts.
The reasons are obvious. Japan and the US are the world's economic giants and , despite current frictions, their relationship is sturdy and growing. Annual two-way trade has reached $60 billion. Together, the two nations account for a staggering 35 percent of global economic output. To this can can be added that the economies of South Korea and many Southeast Asia states also are thriving.
US officials say it is the growing economic weight of Asia - combined with the Soviet Union's outward military thrust in the region - which prompted President Reagan initially to plan a 17-day, five-country swing through the area. That trip was reduced to only two countries when political turmoil erupted in the Philippines following the assassination of opposition leader Benigno Aquino.
Today, administration officials stress, there is scarcely a global issue in which Japan's voice is not important. One aim of Mr. Reagan's talks with Prime Minister Nakasone will be to find areas for expanded collaboration on international economic matters, including the world debt problem, help for the developing countries, and trade. No less is at stake than global stability, US officials say, and Japan has an enormous capacity for constructive action.
Washington gives Japan high marks for its foreign aid effort, and especially for moving to help Egypt and other countries in the Middle East. But it feels Japan could contribute still more to ameliorating the plight of the poorer countries.
The Reagan administration also seeks Japanese diplomatic support in dealing with outward Soviet pressures, as Japan provided in the cases of Afghanistan and Poland. In this connection, President Reagan will stress the theme of working together for peace when he addresses the Japanese Diet (parliament) on Friday.
Conscious of the sensitivities of the Japanese people on the subject of war, Mr. Reagan is expected to deliver a measured address, mentioning the recent Soviet downing of a Korean airliner but not attacking the Soviet Union. An administration official traveling with the President said the US would like to see a stronger Japanese defense effort but that, politically, this might not be a propitious time for such an effort.
''Whatever we ask has to go through the Japanese political system and the bureaucracy,'' he said. ''So we recognize that, as we have to deal with Congress , they have to deal with their political system.''
In noting the new emphasis being given to Asia in US foreign policy, American officials also mention that President Reagan is going to the People's Republic of China in April. Following the current presidential trip, a high White House official will travel to Peking to begin preparations for the journey.