KIEV, Ukraine - Ukraine's Supreme Court said it will not come to a decision today on the political opposition's appeal challenging the validity of last week's disputed presidential election.

The nation's Central Election Commission declared Prime Minister Viktor Yanukovych the winner of the Nov. 21 vote, but opposition candidate Viktor Yushchenko claimed the vote was rigged.

Justice Anatoliy Yarema said the court would give Yanukovych's lawyers until 10 a.m. Tuesday to study additional evidence presented by Yushchenko's team.

Yushchenko's team is asking the court to throw out the results, cancel the election commission's decision and name Yushchenko the victor because he narrowly won the Oct. 31 first round.

Lawmakers in a key pro-Yanukovych eastern province, in turn, called a referendum on autonomy for their region, raising the specter of the nation splitting apart.

The court's ruling could pave the way for a new vote or remove the barrier to the inauguration of Yanukovych, who also has the backing of outgoing President Leonid Kuchma. However, it is not certain the other side would accept the legitimacy of the decision.

If that happens, the ruling could deepen the divide and prolong a crisis that has developed into a tense political tug-of-war between the West and Moscow over Ukraine's future.

Yushchenko urged supporters who have thronged downtown Kiev to stay in the streets. Kuchma had called on the opposition to end its four-day blockade of government buildings, saying compromise is the only solution to the crisis.

Early today, Yushchenko supporters slid down the capital's icy streets, crying "Yushchenko! Yushchenko!" Others, wrapped in thick blankets, stood in line for porridge at the opposition tent camp on Kiev's tree-lined main street.

Yulia Tymoshenko, a top ally of Yushchenko, told a rally of about 100,000 opposition supporters in Kiev's main square that Kuchma had until this evening to fire Yanukovych.

"We know where he is, and we can prevent him from making a single step if he doesn't fulfill our demands," Tymoshenko said.

Her other demands included firing the governors of eastern regions who have threatened to push for self-rule.

The crisis has exacerbated the stark divide between the pro-Russian, heavily industrialized eastern half of Ukraine, where Yanukovych draws his support, and the west, Yushchenko's stronghold including Kiev, which is a traditional center of Ukrainian nationalism.

Apart from Independence Square, protesters continued to pack Kiev's main street, choking off entrances to the Cabinet and presidential administration buildings.

By keeping government employees out of the buildings, the protesters have effectively blocked the work of the government: Finance Minister Mykola Azarov complained Sunday that the blockade was blocking government funds.

Supporters of Yanukovych struck back from Donetsk, his native region and main power base. The regional legislature voted 164-1 to hold a Dec. 5 referendum on autonomy for the province. About 30,000 demonstrators, who gathered outside the legislature building in the city of Donetsk, shouted pro-Yanukovych slogans.

"We won't tolerate what's going on in Ukraine," said Donetsk governor Anatoly Bliznyuk. "We have shown that we are a force to reckon with."

Autonomy for Donetsk would require changing Ukraine's constitution to allow for stronger self-rule for its provinces. While such changes could face serious opposition, the vote suggested Ukraine's rift could widen if the election results are overturned.

The referendum vote came after an urgent meeting attended by Yanukovych and some 3,500 delegates from eastern and southern Ukraine. Participants adopted a resolution threatening moves toward self-rule if the prime minister is denied office.

Borys Kolesnikov, the speaker of the Donetsk regional legislature, warned that a Yushchenko presidency could lead to the formation of an autonomous southeastern republic with its capital in Kharkiv, close to the Russian border.

Tymoshenko accused Kuchma of provoking "attempts to split Ukraine."

She urged the crowds to march to the Supreme Court and the Ukrainian parliament, where Yushchenko's supporters planned to seek a no-confidence vote in Yanukovych's Cabinet.

The Supreme Court said last week that the official results of the election must not be published until it rules on Yushchenko's challenge. Yanukovych cannot formally take office until the results are published.

Under Ukrainian election legislation, the court is unable to rule on the overall results, but can declare the results invalid in individual precincts.

On Saturday, Ukraine's parliament passed a nonbinding resolution declaring the election invalid amid international calls for a new vote.

The United States and other Western nations say the election was marred by massive fraud. Russian President Vladimir Putin openly backed Yanukovych and congratulated him on his victory. The prime minister was expected to pursue closer ties with Moscow, which considers this nation of 48 million people part of its sphere of influence and a buffer between Russia and NATO's eastern flank.

Yushchenko, whose wife is U.S.-born, says he wants to push the country to greater integration with Western Europe, and he has suggested he would seek NATO membership. His critics worry he will alienate Ukraine from Russia, its key trade partner and main energy supplier.