Both the United States and Europe have welcomed Ukraine's announcement of opposition leader Viktor Yushchenko's victory in the presidential election while ex-prime minister Viktor Yanukovych refused to concede.

"We welcome the certification by the Central Election Commission of Viktor Yushchenko as the winner of the Dec. 26 re-vote. This is a momentous step in the Ukrainian people's struggle for democracy," US State Department spokesman Richard Boucher said Tuesday.

Ukraine's Central Election Commission on Monday formally declared Yushchenko's election victory with 51.99 percent of the vote.

The announcement paves the way for parliament to set a date for Yushchenko's inauguration.

However, Boucher declined to congratulate Yushchenko on his election victory, saying: "We don't plan on congratulating a winner until all the legal challenges have been resolved and the election commission has published its final results."

"We understand the Ukrainian law now allows the challenger seven days to submit an appeal to the Supreme Court. And we also understand from press reports that Prime Minister Yanukovych is saying that he will appeal to the Supreme Court," Boucher said.

On the same day, European Union (EU) foreign policy chief Javier Solana welcomed the confirmation of Yushchenko's victory and hailed his "wisdom" in seeking to heal divisions left by the elections.

"The election results give you a strong mandate to meet the great popular expectations of the Ukrainian people," said Solana, who played a key role in mediating the agreement to organize a re-run after a contested Nov. 21 poll which gave victory to Yanukovych

"Your wisdom in working for all Ukrainians and for good relations with all of Ukraine's neighbors will prove to be a soundinvestment for future prosperity," he added.

The Organization for Security and Cooperation in Europe (OSCE),which monitored the Ukrainian presidential election, on Tuesday also congratulated Yushchenko.

However, Yanukovych, who, according to the electoral commission,received 44.20 percent of the vote, announced Tuesday that he willappeal to the Supreme Court over the official results. If the appeal is unsuccessful, he said, he will take the fight to the European Court of Human Rights.

"We will never agree with these results," Yanukovych told a press conference in Kiev. "We cannot recognize the legitimacy of the president and the election."

"The results declared by the Central Election Commission give us a convincing basis to file a complaint with the Supreme Court,"Yanukovych said.

Meanwhile, Ukraine's Supreme Court on Tuesday prohibited the Central Election Commission and the two official gazettes from officially publishing the final results before the court examines the appeal of Yanukovych.

Under Ukraine's law, the final results must be approved by the Supreme Court and published in two official newspapers before Yushchenko can be inaugurated.

Yanukovych won a disputed presidential runoff on Nov. 21, triggering weeks of protests by Yushchenko's supporters. The Supreme Court later annulled the results and ruled for a re-vote on Dec. 26.