Thousands of ethnic Serbs gathered in the southern province of Kosovo last Friday, determined to travel to Belgrade to lodge a protest at this week's communist party congress. About 600, from the village of Batusi, were planning to leave for good because of rising ethnic violence.

Authorities, alarmed at the prospect of an emotional demonstration in Belgrade, surrounded the crowd with militia, suspended northbound transport and prevailed on the restless Serbs to stay home. Official accounts later said the crowd had been persuaded to disperse. But journalists and dissident sources in Belgrade said they had been told by witnesses that police swung clubs and barricaded roads to stop groups of migrants.

Transport between Kosovo and Belgrade remained restricted all week, allowing the ruling League of Communists to stage a peaceful festival of speeches. Three days' debate, with more than 1,000 speakers, has produced no new economic or political initiatives, and none is expected before the congress closes Saturday.

Yet the image of police lines keeping angry crowds away from Belgrade has reinforced a growing sense of concern here. "The problem for us is to start acting," said Ivan Stambolic, president of the Serbian Republic. "The people are no longer interested in what we are talking about, but what we have done."

For all its lack of action, the congress has underlined a broad consensus on the nature of the crisis facing this nonaligned country straddling Europe's East-West divide. Since the death of postwar leader Tito in 1980, the debt-burdened economy has stagnated and political power has atomized as each of Yugoslavia's six republics and two autonomous provinces has pursued autarchic nationalist policies.

With its marketplace shattered, the country has become little more than an unhappy alliance of ministates. Each boasts a powerful bureaucracy resistant to national authority, economic integration or even substantial trade with other republics. In the last three years, only the intense pressure of outside forces such as the International Monetary Fund has made possible the adoption of nationwide stabilization policies.

Though Yugoslavs have managed to live with the disorder for years, government leaders and dissidents alike say the dangers of national upheaval are greater than ever. The party's official report cited "great dissatisfaction in the working class" over living standards that have declined 30 percent in six years and inflation that has reached 85 percent. More than 1 million are now unemployed.

Then there is Kosovo, where pressure on Serbs from the dominant ethnic Albanian population has provoked violence and mass emigration, and stirred high emotions among Yugoslavia's 9 million Serbs. "Kosovo is the detonator of the crisis in Yugoslavia," said Milovan Djilas, the country's best-known dissident. "It is not the worst problem, but it is symptomatic to people of everything that has gone wrong."

The danger, say Yugoslav analysts, is that Kosovo will cause a destructive surge of nationalism in Serbia, the largest republic and traditionally the strongest political base of a united Yugoslavia.

Party officials are inclined to agree with their critics. "The illusions we had were eliminated," said Stambolic, the most important Serbian leader. " . . . Now everybody is conscious of the fact that changes are needed."

Nevertheless, there is wide disagreement on what kind of reforms will work and how they can be pursued. Frustrated officials point out that the system itself blocks radical shifts by requiring that all major initiatives be adopted by "consensus" -- or unanimous agreement -- by the various republics.

Many party activists, as well as U.S. officials concerned about the consequences of destabilization in Yugoslavia, have focused their hopes for improvement on the new prime minister, Branko Mikulic, a 57-year-old administrative strongman from Bosnia-Herzegovina.

Mikulic, arguably the most powerful single official in the chaotic political landscape, delivered a forceful address to the congress last night, making clear his intention to force the implementation of nationwide stabilization policies on the governments of the republics.

"Some individuals oppose changes in order to protect local interests," Mikulic declared. ". . . I think it is time we asked ourselves whether, and how long, we can tolerate everyone having their own attitude to adopted policies without being bound to implement them."

Mikulic appears to be leading the party toward a strategy of postponing nettlesome questions of political reorganization in favor of strong attempts to stabilize and unify the economies of the republics through nationwide market competition.

The problem with such an approach, critics say, is that it ignores the political barriers to implementing even basic economic measures. "It was the political system, the local party bureaucracies, that broke up the market in the first place," said Mihajlo Markovic, a prominent dissident. "The problem of the party is that at the moment, significant political reform is impossible because you have a deadlock. And yet without political reform, real economic stabilization isn't possible."

Party activists and their critics both foresee a desperate game of political brinksmanship. As economic and social pressures mount, they say, the republics' leaders may finally sacrifice local interests rather than risk national anarchy.

If they refuse, several analysts said, only the Army may be strong enough to enforce Yugoslav unity. But if that happened, said Markovic, "we would lose a lot of our freedom."