SPLIT, Yugoslavia (AP) _ Leaders of Yugoslavia's contentious republics failed Thursday to reach agreement on the country's future. Slovenia's president said his republic was ''one step closer'' to secession.

But Mario Nobilo, an aide to Croatian President Franjo Tudjman, said the leaders of the six republics had come through their meeting a ''psychological step closer by having a frank and open dialogue,'' although Nobilo described the session as ''stormy.''

Fears of civil war and military intervention had subsided earlier in the week when the leaders of the republics agreed to a series of negotiations, with the first session Thursday. But virtually the only accord to emerge was that further talks would be held. No date was set for the next meeting.

When the six gathered for an unprecedented joint news conference, their political differences were as apparent as ever.

Croatia and Slovenia, where center-right governments ousted Communists in elections last spring, want to turn Yugoslavia into a loose confederation of states.

Serbia, where President Slobodan Milosevic's renamed Communists were re- elected last December, has insisted on keeping a tight federation ruled from Belgrade, the Serbian and Yugoslav capital.

Milosevic, speaking Thursday at his first news conference since taking power in 1987, defended his idea of maintaining the federation. He also attacked the free-market reforms of embattled federal Premier Ante Markovic.

Backed by President Momir Bulatovic of Montenegro, Serbia's traditional ally, Milosevic said all Yugoslavs should decide on the country's future political structure in a referendum.

But Slovenian leader Milan Kucan, whose tiny, prosperous northern republic has gone furthest in its drive for independence, said such a referendum would not be ''a democratic solution.''

The official Tanjug news agency said the Slovenian parliament opened and then postponed a debate on secession pending the outcome of the national meeting.

Serbia is the largest republic, with 9 million of Yugoslavia's 24 million population. Croats make up more than 5 million, and Slovenes about 2 million people.

Kucan, the Slovenian leader, said Yugoslavia's crisis was ''getting deeper and deeper every day.''

Kucan later told The Associated Press that Slovenia did ''not want to stay in this kind of Yugoslavia.'' He added: ''I am not optimistic for the outcome of the crisis.''

More than 90 percent of Slovenians voted Dec. 23 in a plebiscite to leave Yugoslavia by June if the federation is not reshaped. Later, Slovenian officials they said could leave even sooner.

''After these negotiations, Slovenia is one step closer to implementing the result of the plebiscite,'' Kucan said.

During the first part of Thursday's seven-hour session, the presidents discussed Markovic's future as premier, but agreed to postpone any decision until the next meeting is held, in Serbia. No date was set for the next meeting.

Tudjman, the meeting's host, argued with Milosevic at the news conference over the future of Croatia's 550,000-member ethnic Serb minority.

Milosevic has threatened to expand Serbia's borders to include ethnic Serbs in other republics if negotiations break down.

Thursday's summit was held at the Villa Dalmatia, a residence of the late President Josip Broz Tito, who died in 1980. The delegates sat at a table marked with the flags of individual republics, not of Yugoslavia.

Western European and U.S. leaders support Markovic, the premier, and have stressed that they want the Yugoslav federation to remain together.

President Bush, in a letter to the Yugoslavian premier published Thursday, urged the nation's leaders to resolve their differences ''within a single, democratic Yugoslavia.''

Tudjman and Milosevic reportedly agreed Monday that Markovic should be sacked. Croatian officials confirmed he might be ousted soon.