Secretary of State Colin Powell (search) said Wednesday the United States does not consider legitimate the results of elections in Ukraine, which the opposition says was marred by fraud.
He challenged leaders of the former Soviet bloc nation "to decide whether they are on the side of democracy or not."
"If the Ukrainian government does not act immediately and responsibly there will be consequences for our relationship, for Ukraine's hopes for a Euro-Atlantic integration and for individuals responsible for perpetrating fraud," Powell said.
The secretary was not explicit. However, the United States often revokes the U.S. visas of officials involved in perpetrating fraudulent elections in foreign countries.
Another option would be to refuse Ukrainian entry into Euro-Atlantic organizations such as NATO.
Powell said he spoke with outgoing Ukraine President Leonid Kuchma (search) and urged that his government not crack down on demonstrators. He also spoke with other regional leaders, including Russian Foreign Minister Sergey Lavrov (search).
Powell spoke to reporters shortly after election officials in Ukraine declared that Kremlin-backed Prime Minister Viktor Yanukovych (search) won the election over opposition candidate Viktor Yushchenko (search).
The announcement raised fears of violence in Kiev, where tens of thousands of demonstrators have been demanding that the results be overturned.
"We cannot accept this result as legitimate, because it does not meet international standards and because there has not been an investigation of the numerous and credible reports of fraud and abuse," Powell said.
The crisis in Ukraine also posed a dilemma for the United States. Ukraine has supported the military campaign in Iraq, and contributed 1,600 soldiers to the coalition. Yushchenko had said that if elected, he would withdraw Ukraine's troops.
Powell did not elaborate about his conversation with Lavrov, but said he advocated a solution to the crisis in Ukraine that is "based on the law, using legal procedures."
The State Department confirmed Tuesday that it had summoned the Russian ambassador and discussed Ukraine. The Kremlin described the meeting as "unprecedented interference" in another country's affairs.
Putin has openly backed Yanukovych, who promises to make Russian an official language in Ukraine. The Russian leader made well-publicized state visits before both rounds in the Ukrainian elections.
Powell said Wednesday he discussed the elections with European Union officials and with Polish President Aleksander Kwasniewski (search), who has offered to mediate.