LJUBLJANA, YUGOSLAVIA, DEC. 23 -- Residents of Slovenia, the most Westernized of Yugoslavia's six constituent republics, voted overwhelmingly today to give their new nationalist government the authority to declare independence from the ethnically hybrid state unless Yugoslavia is realigned into a much looser confederation of sovereign states.

Defying condemnation of the plebiscite and threats of military intervention by the Yugoslav federal leadership, 88.2 percent of Slovenes cast ballots to authorize secession from the politically troubled Yugoslav federation, and four percent voted against, according to unofficial results tabulated by authorities here in the Slovenian capital. Turnout was 90 percent of the 1.5 million eligible voters. Final official results are expected Monday.

From tiny villages in the shadow of the Alps to towns on the Adriatic coast, Slovenes trooped to the polls throughout the day to cast their ballots in a vote crucial to the continued existence of Yugoslavia, which was created out of the ruins of World War I and transformed into a Communist-led federation after World War II. Some village folk assembled in lightly falling snow to celebrate the occasion with glasses of wine and patriotic songs, while diplomatic observers pronounced it yet another step on the road to the apparent disintegration of Yugoslavia as a political entity.

The enthusiastic response surprised even some government officials who in the weeks leading up to the plebiscite had bombarded voters with messages promoting independence in official broadcast media and newspapers. "I only hope we don't win with 104 percent of the vote," one senior official said jokingly.

Under provisions of the plebiscite, the government now has six months in which to negotiate a last-ditch constitutional compromise mandating near total autonomy for each of the Yugoslav republics, or, failing that, to proclaim Slovenia independent.

Croatia, the second-largest Yugoslav republic and Slovenia's closest neighbor, has declared its support for greater local autonomy within a loose Yugoslav confederation, but Serbia, the largest and most staunchly Communist of the republics, strongly supports the present system of unified rule from Belgrade.

Led by populist President Slobodan Milosevic, Serbia last month slapped a 50 percent surtax on trade with Slovenia and Croatia as punishment for their "anti-constitutional" provocations.

The Slovenian plebiscite coincided with the second round of multi-party elections in Serbia and its closely allied Yugoslav neighbor, Montenegro. Communist and Serbian nationalist candidates won hefty majorities in first-round balloting two weeks ago, and that trend was expected to continue today, giving Milosevic strong support to oppose Slovene and Croatian separatism.

Many Slovenes have long complained that their relatively strong economy has been victimized by its linkage to that of other, less productive Yugoslav republics and have argued for broader ties to the West. "We've been paying too much for too long," said one Ljubljana voter. "We'll be better off on our own."

But others are not so sure. While Slovenia's economy is far more efficient than the Yugoslav average, it is outperformed to the same degree by neighboring Austria and Italy, and critics argue that an independent Slovenia could find itself cut off from Yugoslav markets and unable to pierce Western trade barriers.