WASHINGTON -- In the decade after Chinese leader Deng Xiao-ping came to power in 1979, he broke down the isolation in which China found itself under Mao Tse-tung and set the world's most populous nation on a steady course of ever-growing involvement in world affairs.

Now, this 10-year phenomenon has come to a halt. During the six months since the Chinese regime called in the People's Liberation Army to suppress pro-democracy demonstrations in Tian An Men Square, foreign governments and leaders have put distance between themselves and China, leaving China largely out in the cold.

One of the casualties of last spring's political turmoil, it now seems, was Deng's long-planned and carefully nurtured plan to develop close interconnections between China and the outside world.

"The Chinese find themselves more and more isolated," says Harry Harding, a China specialist at the Brookings Institution. "They're left with Romania, North Korea and Cuba, which is an alignment that only illustrates China's isolation. For any thinking Chinese, it's an embarrassment. This is what China's reduced to, welcoming Fidel Castro?"

It is unclear whether the visit to Beijing over the weekend by U.S. National Security Adviser Brent Scowcroft and Deputy Secretary of State Lawrence S. Eagleburger will succeed in reversing China's slide into isolation, or whether it will turn out to have been a failed attempt to turn things around.

Consider what has happened to China since the political upheavals last June:

-- The leading industrialized democracies of the world--including the United States, Western European nations and Japan--joined together to impose a package of economic sanctions, including an extremely costly suspension of international lending to China.

-- The Soviet Union has become at least as threatening ideologically as the West, because President Mikhail S. Gorbachev is willing to tolerate dissent and political change to a degree unacceptable to the Chinese leadership. "To the Chinese, if we in the West are the wolf at the front door, Gorbo's the tiger at the back door," observes one senior U.S. official.

-- As recently as October, China had hoped that a bloc of seemingly entrenched East European Communist regimes--East Germany, Czechoslovakia, Bulgaria and Romania--would join with it in resisting the changes that have swept the socialist world. Instead, the hard-line leaders of all but Romania have themselves been forced to give up power.

-- When China was at odds with both the United States and the Soviet Union in times past, China took solace in its close ties with the nations of the Third World. But since June, Third World governments, too, have avoided rushing to China's support.

This fall, in another surprising reversal of the past decade's trends, three Third World countries--Liberia, Grenada and Belize--broke off relations with China and established diplomatic ties with Taiwan, which through the 1980s had been losing international recognition. All three countries are believed to have received substantial economic aid from Taiwan.

"Taiwan's obviously got enough money now to go out and virtually buy diplomatic relations with some Third World countries," observes Bonnie Glaser, who, with her partner, Banning Garrett, is a Washington-based consultant on Chinese foreign policy.

In foreign capitals, even those officials who seek to reverse China's drift toward international isolation acknowledge that the Chinese leadership has become difficult to work with.

"It's like dealing with a small, beleaguered country," says one Bush Administration official who believes that isolation abroad could lead to further political repression inside China. "Except that this one happens to be large, well-equipped and centrally located."

Declares another U.S. official: "We're dealing with a deeply wounded country, led by a rump Old Guard with very little underneath them."

From the perspective of China's current leaders, there was no choice. In their view, China is not purposely withdrawing from the rest of the world; rather, the rest of the world is pulling away from China.

The different viewpoints stem directly from the events at Tian An Men. To many foreign leaders and governments, China's resort to violence to suppress the pro-democracy demonstrations was a flagrant and offensive violation of human rights.

But Chinese officials--who have, in the past, condemned government violence in other countries such as South Africa--insist that what happened at Tian An Men was not the business of any foreign country. Rather, it was "entirely China's internal affair," Communist Party Secretary Jiang Zemin told former President Richard M. Nixon this fall.

Since June, Chinese leaders have gradually developed a broad ideological theory to explain both the turmoil at Tian An Men last summer and the changes now taking place in Eastern Europe.