Russia and the US clashed over their efforts to win influence in Ukraine, with Moscow warning the West against interfering in former Soviet states - a region it considers to be its backyard.
Washington rejected the charges.
In the latest setback for international mediation efforts to reconcile an opposition that has mobilised hundreds of thousands of protesters, President Leonid Kuchma reversed his stance on concessions within a matter of hours on Tuesday.
Last month's election, rigged by the authorities to hand power to Prime Minister Viktor Yanukovich, pushed the country into two weeks of political and economic chaos.
The Supreme Court backed opposition leader Viktor Yushchenko's charges that the poll was tainted by fraud and set a re-run for 26 December.
Some progress appeared to have been made in the early hours of Tuesday after a marathon "round-table" negotiation brokered by European Union foreign policy chief Javier Solana when Kuchma said he would meet two of three opposition demands.
But, in a written statement hours later, he said: "If we are to speak in general terms, no agreement was reached and instead of a statement from the round-table talks, there was simply a statement for the press."
Yushchenko's group is insisting
on the government's dismissal
He said Yushchenko's Our Ukraine group had stalled the talks by insisting on the dismissal of the government, but opposition leader Petro Poroshenko said the authorities were seeking to deepen the crisis.
The economy showed further signs of trouble. The Treasury said the budget deficit widened from zero to $1 billion in September and October, or 2% of gross domestic product.
Cold War tensions
The crisis has also rekindled old Cold War tensions.
Russia, for centuries Ukraine's imperial master, was taken aback by fierce charges from the West of vote rigging in the 21 November poll in which it congratulated its preferred candidate, Yanukovich, even before he was officially named winner.
On Monday, it did an about-turn and dropped public support for him.
On Tuesday, Russian Foreign Minister Sergei Lavrov accused the West of using election monitors to influence domestic affairs - a thinly veiled criticism of what Moscow sees as Western interference in Ukraine.
Powell rejected accusations of
US Secretary of State Colin Powell flatly rejected the suggestion and took issue with Russia on many matters.
"It is not a matter of [spheres] of influence, it is a matter of allowing a country to choose how it wishes to be governed and who it wishes to have as its friends," Powell said on a trip to Bulgaria.
In their stand-off, the opposition is demanding the sacking of the central election commission, new laws to prevent vote-rigging, and Yanukovich's dismissal.
Kuchma, who said after the mediation talks he would agree to the first two demands, wants the opposition to vote for constitutional changes to cut the powers of the next president and give more power to parliament and the prime minister.
The opposition fears Yanukovich might use his government post to help his election bid. Analysts say Kuchma anointed him as a successor and is unlikely to support calls from hardline opponents to prosecute him once he retires.
But it has resisted moves to cut presidential powers.
"Bill 4180 [to curb presidential powers] in its current form, allows parliament to take over practically all presidential powers," Yulia Tymoshenko, a close ally of Yushchenko told Russia's Nezavisimaya Gazeta.
"If we approve it in full, presidential polls lose their point. There will be no difference who is president, because any president after such reform will be a ceremonial figure."