Viktor Yanukovych (search), the losing candidate in Ukraine's presidential vote, said Tuesday he would appeal to the Supreme Court to challenge the official declaration of Viktor Yushchenko's (search) election victory.

Yanukovych, who is backed by Moscow, said his allies would file a massive appeal to demand "the annulment of the so-called rerun." He described the appeal as "a convincing package of evidence that would prove election fraud" in the Dec. 26 vote.

Late Monday, the Central Election Commission formally declared the Western-leaning Yushchenko the winner 15 days after the rerun of a Nov. 21 vote in which Yanukovych was declared the victor. The Supreme Court annulled the Nov. 21 result after Yushchenko's camp filed appeals alleging massive fraud.

Taras Chornovyl, Yanukovych's campaign manager, said the appeal would be submitted Wednesday afternoon. The timing could indicate Yanukovych is aiming to delay Yushchenko's inauguration as long as possible.

Yanukovych said his team would use "all legal remedies" including an "appeal to a European court if the court does not rule favorably."

But a last-minute change of fortune for Yanukovych appeared unlikely. The Supreme Court on Monday rejected eight minor appeal motions from his camp.

Nestor Shufrich, Yanukovych's representative in the Central Election Commission, suggested earlier that the appeal would focus on an electoral reform, enacted after the Nov. 21 vote, that blocked absentee ballots and home voting — allegedly a prime source of voting abuse.

That measure was overturned by the Constitutional Court just a day before the Dec. 26 rerun and left little time for many old and ailing Ukrainians to make voting arrangements.

The final official tally of the vote showed Yushchenko with 51.99 percent and the Kremlin-favored Yanukovych with 44.2 percent, the Central Election Commission announced late Monday, formally declaring Yushchenko the victor 15 days after the balloting.

But the final results must be approved by the high court and published in two official government newspapers before Yushchenko can be inaugurated, and the Supreme Court said Tuesday that the results cannot be published until it reviews Yanukovych's complaint.

"The Central Election Commission is ordered not to publish the election results in both official newspapers," said court spokeswoman Natalia Sarapyn. The court ruling followed a motion filed by Yanukovych's allies earlier in the day.

European Union foreign policy chief Javier Solana congratulated Yushchenko, saying it was a "strong mandate to meet the great popular expectations of the Ukrainian people."

Italian President Carlo Azeglio Ciampi, Pope John Paul II and Organization for Security and Cooperation in Europe (search) Secretary General Jan Kubis also congratulated Yushchenko.

Backed by hundreds of thousands of protesters, Yushchenko successfully contested the results of the Nov. 21 election. The Supreme Court prohibited official publication of results showing Yanukovych the winner and eventually declared the vote invalid.

International election observers had harshly criticized the Nov. 21 election as a step backward for the ex-Soviet republic, citing widespread incidents of multiple voting and bias by state-run media against Yushchenko.

Yanukovych's campaign manager threatened that angry supporters from the candidate's stronghold, the eastern Donetsk region, could pour into Kiev to protest a Yushchenko victory but there were no expectations of any rallies on Tuesday.

Ukraine's political tensions derive partly from an ethnic fault line between the country's east, which is heavily Russian-speaking, and the center and west, where Ukrainian nationalist spirit is strong.

Yanukovych supporters fear a Yushchenko presidency could marginalize Russian-speakers and heighten tensions with Moscow, which is Ukraine's largest trading partner and the source of much of its gas and oil.

Yushchenko has vowed to work against the primarily eastern "clans" that control much of industry and have concentrated wealth in a small number of hands. As president he is widely expected to fight corruption.