As the search for a compromise continued in Kiev, Putin warned against foreign interference in the new ballot but pledged that Russia would abide by the vote results.
Powell, in Bulgaria for a meeting of the Organization for Security and Cooperation in Europe, rejected Putin's accusations of Western interference.
"What we have seen is not anyone interfering in democracy," he said Tuesday. "What we have seen is the international community coming together to support democracy."
Backers of Western-leaning opposition leader Viktor Yushchenko — in their third-straight week of protests in a sprawling tent camp in downtown Kiev — barricaded the entrance to the Cabinet building, determined not to let "a single bureaucrat enter."
The opposition leader has urged his supporters to remain in the tent camp and continue blockading official buildings until outgoing President Leonid Kuchma fires the winner of the disputed election, Kremlin-backed Prime Minister Viktor Yanukovych, and stops stalling changes in the electoral system.
Supporters of Yushchenko said the changes are necessary to close loopholes for fraud that marred the Nov. 21 presidential runoff. Evidence of vote-rigging prompted the Supreme Court to order the rerun.
But a loose coalition of communists, socialists and pro-government factions said they would only pass the electoral changes simultaneously with a constitutional reform that would trim presidential powers. Yushchenko has opposed the changes, saying Kuchma's allies fear his victory and want to curb his authority, if he were elected.
Putin has dented his prestige and squandered influence by backing the wrong side in political clashes in Ukraine and in the breakaway Georgian province of Abkhazia, analysts say.
Putin tried to put the best face on things in his comments Monday on the Ukrainian Supreme Court's decision to annul the victory of Kremlin-backed presidential candidate Viktor Yanukovych.
He sternly warned foreign countries not to interfere in the revote — scheduled for Dec. 26 against opposition leader Viktor Yushchenko — and said Russia would work with whoever won.
"Of course we will ... accept the will of any nation in the former Soviet space, and will work with any elected leader," Putin said.
That couldn't hide an embarrassing — and largely self-inflicted — defeat for Putin, who appeared at Yanukovych's side during the campaign and only last week mocked the idea of a new presidential runoff.
The events have frayed his carefully tended relationships with the European Union and the United States, both of which refused to recognize the election and pointed to evidence of widespread fraud — after Putin had congratulated Yanukovych.
Closer to home, it showed Russia as ineffectual in dealings with other former members of the Soviet Union, where it seeks a dominant role. The Ukraine debacle came amid a fumbled attempt to push its own candidate for president of the breakaway region of Abkhazia in Georgia.
And it follows last year's revolution in Georgia, where Russia couldn't stop reformer Mikhail Saakashvili — who wants to move closer to the West — from winning power amid protest over fraudulent elections there.