Senior Soviet and Chinese officials have been meeting this week in Beijing for discussions that may well lay the groundwork for peace in Cambodia. While an end to the Cambodian conflict is obviously important, the meetings have taken on an even greater significance.That both powers would agree to participate underscores the remarkable political changes unleashed in the Far East by the diplomacy of Mikhail Gorbachev.

The prospect of Chinese-Soviet d'etente, peace in Indochina, and even improved Soviet-Japanese relations all reflect a reshaping of the political landscape two years after Gorbachev outlined a fresh approach.

The new Soviet diplomacy, when combined with growing Asian nationalism and fears of American protectionism, poses new challenges to American interests.

Until recently, Moscow's Asian policy consisted of an unprecedented military buildup and imperious tactics that left many states deeply suspicious of Soviet intentions.

Moscow's bluster had the unintended consequence of bolstering American interests, as Washington forged closer ties to China and to Asean (the Association of Southeast Asian Nations), and solidified a strategic partnership with Japan.

At the same time, most conflicts in Asia were fought between Communist countries: China and the Soviet Union, China and Vietnam and Vietnam and Cambodia.

On the surface, at least, Gorbachev has changed all that. He has cleaned house in his foreign policy bureaucracy, stocking his Asian embassies with sophisticated diplomats carrying out a charm offensive previously reserved for Western Europe.

More important, he has reinforced the new style and tactics with important concessions - most notably, retreating from Afghanistan, removing SS-20 missiles in the Soviet Far East, and pressuring Vietnam to withdraw from Cambodia.

The fruits of Gorbachev's efforts are readily discernible, beginning with China - the centerpiece of his Asian policy.

There are strong signals that next year will bring a Chinese-Soviet summit meeting - the first in 30 years - which will formalize the rapprochement, complete with restored party-to-party relations and even military contacts.

And with a Cambodian resolution now within sight, Moscow has emerged as a key power broker with an opportunity for new relations with the non-Communist states of the region. Change is stirring even in Moscow's relations with Japan, although the signs are still faint.

Mr. Gorbachev is also championing antinuclear forces in the Pacific, urging the creation of nuclear-free zones and curbs on military activity everywhere in the region where Moscow has little or no presence.

In this changing security environment, with Moscow viewed as part threat, part partner, the traditional American balancing role is more crucial to stability than ever. Yet, while few allies desire an American retreat, talk of burden-sharing and of American decline is casting a shadow over America's role.

The U.S. might alter its policy with the acceptance of Moscow's legitimate role in the region, distinguishing that from such truly threatening behavior as new military deployments or the backing of Communist insurgencies.

That would help redirect superpower competition into the economic and political realms. Here, Washington, as the underwriter of East Asia's dynamism, has a decided edge, especially as the novelty of Moscow's joining the game wears thin.