The State Department called on the government of Ukraine Monday to investigate allegations of fraud in its presidential elections or risk a changed relationship with the United States.

Echoing criticism by the European Union, the Organization for Security and Cooperation in Europe (search), Freedom House (search) and others, spokesman Adam Ereli said the United States was deeply concerned and called on Ukrainian authorities "to act to ensure an outcome that reflects the will of the Ukrainian people."

The State Department is not calling for new elections and it is not too late to address concerns, but "quick action on the part of the government of Ukraine is required," Ereli said

Otherwise, he said, "we would consider the results tarnished and would have to consider what responses in the relationship would be appropriate."

In Ukraine, announcement by the elections commission that Kremlin-backed Prime Minister Viktor Yanukovych (search) was ahead of reformist candidate Viktor Yushchenko (search) with nearly all the votes counted evoked widespread dismay and anger among the former Soviet republic's 48 million people.

Russian President Vladimir Putin (search) sent a statement to Yanukovych late Monday to congratulate him on the result, Russian news agencies reported, but a group of international observers described Sunday's balloting as severely flawed.

Sen. Richard Lugar (search), R-Ind., chairman of the U.S. Senate's foreign relations committee, said in Kiev there had been "a concerted and forceful program of election-day fraud and abuse." He called on outgoing President Leonid Kuchma (search) "to view all of this and take decisive action in the best interests of the country."

Ereli said he did not have any comment on Russian activities, nor did he say what action the United States might take against Ukraine.

However, Anders Aslund, of the Carnegie Endowment for International Peace (search), said "the election was stolen" and that Russia had done whatever it could in behalf of Yanukovych, including two visits by Putin, who campaigned for him.

"It was stolen," Aslund said of the election. Exit polls suggest Yushchenko would have won by 11 percent, he said.

"This is very serious," the director of Carnegie's Eurasian program said in an interview. "I don't think this will work. I think it is good that the West is protesting."

The Texas-sized country of 47 million is one of the biggest recipients of U.S. assistance. The State Department has openly offered to help Ukraine join European institutions if the elections met international standards.

Ukraine is a staunch supporter of the U.S. campaign against insurgents in Iraq. It has contributed 1,600 troops to the U.S.-led coalition.

"Obviously, passions are running high," Ereli said. "The United States, in Ukraine as elsewhere, is a passionate supporter of the right of people to express their opinions freely and peacefully." he said.

"It is our position that the will of the people in these elections needs to be respected and the process needs to be peaceful," the U.S. official said.