Declaring there was strong evidence of fraud, the White House urged Ukraine (search) not to certify the results of a run-off presidential election that favored pro-Russia Prime Minister Viktor Yanukovych (search).

The State Department also confirmed it had summoned the Russian ambassador and discussed Ukraine, and the Kremlin described the meeting as "unprecedented interference" in another country's affairs.

The harsh words were exchanged as four Ukrainian diplomats in Washington, in an unusual show of independence, accused their government of subverting the will of the people to favor Yanukovych.

The diplomats said in a signed declaration that voters were subjected to incessant threats, terror and massive fraud. "We cannot quietly look away as Ukraine's future is buried along with the future of our children," the diplomats said.

The United States is deeply concerned about how the election was conducted, spokeswoman Claire Buchan said Tuesday in Crawford, Texas, where President Bush (search) is on a Thanksgiving holiday.

The State Department renewed its demand for a complete and immediate investigation. Elizabeth Jones, assistant secretary of state for European affairs, called in Ukraine's ambassador, Mikhailo Reznik, on Monday and again on Tuesday to underscore U.S. demands for an inquiry and to warn that U.S. relations with Kiev could be damaged.

In the Ukrainian capital, where some 200,000 protesters massed in the streets, U.S. Ambassador John Herbst registered parallel complaints with the prime minister's office, members of parliament and the Ukrainian Foreign Ministry.

There, President Leonid Kuchma, appearing on state television, derided the demonstrators as "political farce" and said the consequences could be extremely dangerous.

But Kuchma called for negotiations among all sides in order to get out of "this crisis."

The Ukrainian diplomats expressed their solidarity with the protesters in challenging "the violation of our citizens' right to elect a president by democratic means."

"We cannot remain silent," they said. "Guided by our conscience, our professional pride and our oath of loyalty to serve the Ukrainian state, we express our solidarity with the voice of the Ukrainian people."

The diplomats demanded "that the results of the election reflect the true will of the people."

The statement was signed by counselors Oleksandr V. Shcherba, Volodymyr M. Chumak and Oleksandr Potiekhin; and Second Secretary Yuriy B. Parkhomenko.