The end of the Cold War has prompted a broad transformation of political alignments in East Asia that have made the United States the "outside power of choice," as one senior U.S. official put it.

With Soviet influence on the wane, Asian leaders long fearful of Chinese domination or Japanese expansionism are viewing the U.S. economic and military presence as a convenient counterweight to both.

Asia's shifting power relationships are expected to continue or even accelerate in the next few years as a generation of aging leaders in Indonesia, Singapore, China, Vietnam and North Korea leaves the stage and a new generation jockeys for advantage and security.

In this year alone, there have been major changes. The Soviet Union and South Korea have established formal ties, while Soviet relations with North Korea have deteriorated. China and South Korea have opened trade offices and China has instituted formal ties with Indonesia and Singapore. Vietnamese Communist Party chief Nguyen Van Linh has offered Tokyo and Washington the use of the U.S.-built base at Cam Ranh Bay.

Such changes reflect a situation in which economic imperatives are replacing ideology as a driving force, in which security interests are viewed as much in economic as in military terms.

"Territorial and military conflicts are being subordinated to the economic interests of the countries," said Donald S. Zagoria, specialist on Asia and a professor at Hunter College. He said this trend is what gives the United States substantial leverage over China, Vietnam and the Soviet Union, as potentially the primary power broker for the region. All three nations "want to join the Pacific economy," he said.

Japanese officials, in recent interviews, acknowledged the concerns of their neighbors about Japan's strength and welcomed U.S. involvement in the region as a way of assuaging such fears.

"It is in the interest of all the countries in the region for the United States to stay" engaged both militarily and economically, one Japanese official said. "It is the strong wish of Japan to see it {the U.S. role} maintained. No one else can play that role" as a balancing force in the region, the official said.

"The fact is that no power other than the United States is now able or welcome to play the role of regional balancer," Assistant Secretary of State Richard Solomon said in a recent speech in San Diego.

As one U.S. official put it, the United States has become "everyone's Linus blanket." But U.S. policy-makers are still grappling with how to reshape America's role in the face of Asia's new realities.

Militarily, the United States has begun to scale back somewhat in Korea and is moving to an air and naval presence based on "access rights" in several ports in Southeast Asia rather than a massive military presence in the Philippines. The United States, in negotiations with the Philippines over the future of its six military bases there, has already agreed to remove all fighter aircraft from the country by next September.

"With the Soviets winding down," one State Department official said, "we have to maintain a credible military presence in the region. But what do we need to be credible? We haven't figured that out yet."

U.S. trade with the Pacific nations, at $300 billion last year, is about 50 percent greater than U.S. trade across the Atlantic. "We can leverage our substantial influence in the Pacific economy into a resolution of the military and territorial conflicts in Asia and the remnants of the Cold War," Zagoria said.

This might include requiring North Korea to disarm or dismantle its troubling nuclear program, Vietnam to help settle the war in Cambodia and account for missing American servicemen, or China and the Soviet Union to pursue economic and political reforms, Zagoria said.

U.S., Soviet, Japanese and Chinese officials said in recent interviews that except possibly for the Korean peninsula there appears to be no immediate security threats in the region.

"We view nuclear proliferation on the Korean peninsula as the number one threat to stability in East Asia," Solomon said in San Diego.

But Hong Koo Lee, an adviser to South Korean President Roh Tae Woo, while not minimizing the danger, appeared to take a more sanguine approach to the North, including the possibility of reunification with a country run for four decades by hard-line communist Kim Il Sung.

"North Korea can't make up its mind whether it wants an arms reduction treaty or it wants South Korea to disintegrate," Lee said in a recent speech in Washington. "They want to buy time. We are telling them that we can wait, take your time," he said. "We think some sort of political solution {to unification} will emerge naturally," he said, adding that he detected signs that the North's leaders "have become a bit more reasonable . . . they are mellowing."

Another potential security problem is the 12-year-old Cambodian civil war, long fueled by regional competition among China, Vietnam and Hanoi's patron, the Soviet Union. But with the Soviets retreating militarily and economically, Cambodia's importance seems to wane.

A Chinese diplomat recently dismissed the Cambodian conflict with a wave of his hand, calling it a holdover from another era. "It is not in our interest to have fighting continue in Cambodia," he said. U.S. sources say the Soviets and Chinese have been cooperating extensively in efforts to resolve the war under a United Nations plan. "Cambodia will be settled; Korea will reunify," a Soviet expert on Asia said in an interview.

China's mounting economic troubles and its diplomatic isolation after last year's crackdown on the pro-democracy movement are pushing it toward trying to improve relations and trade throughout the region -- with the Soviets, Vietnam, Japan and Taiwan. The Chinese have reduced their troops on the Soviet border by 1 million, the Soviets have reduced theirs by 240,000.

Economic collapse in Vietnam has lessened fears among leaders in Indochina that Vietnam, with its huge army, could dominate the region any time soon.

The Soviet Union, both U.S. and Soviet officials agree, is pushing hard to resolve any obstacle to Soviet membership in the region's financial and political institutions, such as the Asian Development Bank or the 12-nation Asia-Pacific Economic Cooperation.

Moscow's and Washington's views toward the region are remarkably similar, with the Soviets supporting Korean unification and insisting North Korea end its nuclear program without trying to tie it to the presence of U.S. forces in the South. The Soviets have stepped up trade with China and have indirect trade relations with Taiwan.

The Soviet Union and Japan are moving quickly to improve relations and sign a peace treaty formally ending World War II. A Soviet-Japanese dispute over four northern islands held by the Soviet Union remains the major barrier to Japanese agreement to full Soviet participation in the regional economy. But working groups of experts from each country have been studying proposals to resolve the issue, Soviet and Japanese officials said. Soviet President Mikhail Gorbachev's scheduled April visit to Japan is likely to accelerate the effort.

Japan, which had conditioned any improvements in relations on a return of the "Northern Territories," has discussed technical aid and economic exchanges with the Soviet Union. Japanese officials said on Nov. 8 that they were considering giving food aid if Soviet food shortages become critical.

Asian and Western analysts said they are optimistic about the prospects for continued economic and political progress in Asia, expecting communist economic systems to break down much as they did in Eastern Europe.

A major difference, however, is that political reform in Asia is likely to occur more slowly because communist leaders there -- especially in China, Vietnam and North Korea -- have substantial claim to nationalist credentials, giving them a popular legitimacy their counterparts in Eastern Europe never had.

Some analysts also worry that the end of the ideological overlay of the Cold War on regional politics may bring the reemergence of ancient antagonisms and regional rivalries.

Last month, for example, an old territorial dispute flared up among Taiwan, China and Japan over five tiny, uninhabited islands and three coral reefs in the East China Sea about 220 miles east of the Chinese mainland.

All three countries claim the islands, called the Senkaku Islands in Japanese and the Diaoyutai in Chinese. In 1972, when China and Japan reestablished relations, they agreed to defer questions on sovereignty.

Six years later, a right-wing Japanese group erected a lighthouse on one of the rocky islands, but little was heard about them after that until Japan's maritime agency last month said it was granting official status to the lighthouse. That sparked an uproar in Taiwan, where an opposition politician led athletes from a sports festival ashore to plant a torch. Japanese coast guard ships chased away the two Taiwanese fishing vessels as the episode provoked egg-throwing and flag-burning demonstrations against Japan in Hong Kong and Taiwan.

The incident was quickly played down by the three governments but exposed deep-seated fears of Japan's intentions in the region, suspicions that are often voiced in Indochina and Southeast Asia in general.

One U.S. official, noting the region's ethnic and national rivalries, said, "It's visceral out there," adding that those antagonisms could be fanned at any time by politicians seeking to score points with their constituencies. Tension over the ownership of the Spratley Islands, claimed by China and Vietnam, could also become a flashpoint.

Other analysts said the region's economic boom and prospects for further growth will smother potential conflict. "The Chinese have $20 billion in trade with Japan," Zagoria said, "and they are not about to let that go by the board just for a few islands. In this modern world, territory is not as important for anyone as it was in previous centuries. Territory is losing its strategic importance."

U.S. and Asian officials continue to be concerned about the possibility of turmoil in both the Soviet Union and China as the two nations attempt to cope with mounting economic and political problems.

U.S. officials also point to Taiwan, where democratization has revealed some popular support for Taiwanese independence, as a potential source of conflict.

But "for the United States," one senior U.S. official said, "Asia presents possibilities, not problems. The real question is not whether Asia will recognize us as an Asian power but whether we recognize ourselves as an Asian power."