BELGRADE, JUNE 21 -- The leaders of Yugoslavia's separatist republics rebuffed an appeal for national unity today from Secretary of State James A. Baker III, who warned them of the "dangers of disintegration of this country" and declared that the United States would not recognize their independence if they left the Yugoslav federation.

After a day of talks here with Prime Minister Ante Markovic and separate meetings with leaders of the country's six constituent republics, Baker said that "what I learned here today has not allayed my concerns" that Yugoslavia is heading for a violent breakup that could have "very tragic consequences" for the country and for Europe.

"We worry, frankly, about history repeating itself," Baker said, alluding to the feud between Serbia -- now the largest Yugoslav republic -- and Austria-Hungary that touched off World War I in 1914.

But Baker's warnings appeared to have little immediate impact, and the northwestern republics of Slovenia and Croatia are expected to issue formal declarations of independence next week. Although neither republic will leave the Yugoslav federation immediately, the declarations will start a process of disengagement and ultimate secession if a compromise with the other four republics is not reached.

Slovenian President Milan Kucan was asked by reporters if anything Baker could say would dissuade his republic from declaring independence, and he replied that he hoped the secretary was bringing him the "good news" that "all the nations of Yugoslavia may live as they wish."

Asked if he meant that Slovenia should be an independent nation, Kucan said: "Yes . . . an independent nation, which out of its own will has ties to other nations . . . the same way as other European nations." Later, Kucan said Baker had made clear to him that neither the United States nor the European Community would recognize an independent Slovenia.

At a news conference tonight with Yugoslav Foreign Minister Budimir Loncar, Baker reiterated his warning that the United States would not recognize Slovenia and Croatia if they declared their independence, and he urged leaders of the two republics to "avoid unilateral actions" that could preempt efforts to find a peaceful solution to the present crisis.

Baker also called on the leaders of all six republics to respect the human rights of the diverse ethnic and religious groups living in their jurisdictions and to move quickly to end the political stalemate that has left the country without a head of state for five weeks. But while the United States would continue to seek a dialogue among the republics, Baker said, "in the end, it's really going to be up to the people of Yugoslavia" to reconcile their differences.

Slovenia and Croatia, which are controlled by strong, democratically elected nationalist governments that ended communist rule in both republics last year, have been seeking to transform Yugoslavia into a loose confederation of sovereign states. They have been opposed by Marxist Serbia and its close ally, the republic of Montenegro, which are demanding a continuation of strong centralized rule from Belgrade, the capital of both Yugoslavia and the Serbian republic.

Yugoslavia's multi-ethnic composition has made the question of independence for some republics extremely difficult. Croatia, for example, includes a sizeable population of Serbs who have said they do not want to be part of an independent Croatia and have, in fact, declared a 30-by-70-mile swath of Croatia to be Serbian territory. Ethnic violence and political discord between Serbs and Croats -- the country's two largest cultural groups -- have intensified over the last year as elections in the republics brought to power leaders who are now spearheading nationalist independence movements.

Serbian President Slobodan Milosevic, a longtime communist, has pursued a vehement course of opposition to Croatia over the political future of Yugoslavia, and in a separate meeting with Baker today he reiterated his belief that the member republics should "not . . . liquidate the country as a state." Speaking to reporters, he said Yugoslavia must maintain "minimal functions," such as defense, foreign affairs, human-rights protection and "one market with a central bank." These are precisely the functions that the secessionist republics plan to assume themselves.

European leaders had earlier appealed to the feuding Yugoslavs to avoid a breakup of the country, which they say could ignite ethnic turmoil elsewhere in Eastern and Central Europe. In addition, leaders of the European Community have warned the Yugoslav republics that secession would risk their economic ties to the West.

In Berlin this week, foreign ministers from the 35-nation pan-European Conference on Security and Cooperation in Europe issued an appeal to the Yugoslavs to resolve their differences through peaceful negotiation, but the mood here seems to be to ignore such pleas. "The leaders of Yugoslavia's republics have not paid much attention so far to such general messages," wrote Belgrade newspaper commentator Julijana Mojsilovic this week. Other newspapers have portrayed Baker's visit here essentially as coming too late to make a difference.

The latest crisis has been over the rotating chairmanship of Yugoslavia's collective federal presidency. The office has been vacant since May 15 when a Croat was to have succeeded a Serb to the one-year post in a ceremony viewed as a mere formality. But the transfer was blocked by Serbia, provoking a constitutional deadlock that remains unresolved.