Ukrainian lawmakers have failed to adopt election law changes the opposition says are needed to avert fraud in a repeat presidential run-off.
Yushchenko urged his supporters to continue mass rallies
The emergency session was adjourned for 10 days because of a rift among several opposition factions on separate bills aimed at trimming presidential powers.
Opposition leader Viktor Yushchenko had pushed for electoral changes ahead of his rematch with PM Viktor Yanukovych.
Outgoing President Leonid Kuchma said the opposition reneged on its pledges.
"The opposition isn't fulfilling practically any of the agreements reached at a round table that involved European politicians," Mr Kuchma said, calling mediators back to Kiev for a new round of talks on Monday.
He spoke a day after the Supreme Court ruled that the 21 November poll, where Mr Yanukovych was officially declared a winner, had been fraudulent.
Mr Yushchenko hailed the ruling - which came after nearly a fortnight of street demonstrations in the capital -
as a victory for Ukraine's democracy.
The Moscow-backed prime minister described it as an unconstitutional measure but said he would contest the re-run.
Mr Yanukovych's supporters - mainly in eastern and southern Ukraine - vowed to vote for him again.
Buoyed by the court's decision, pro-Yushchenko MPs on Saturday pushed for quick passage of bills that would reshuffle the central electoral commission and make other key changes to ensure fair balloting.
Ukraine's Socialists and Communists had earlier promised to vote for the amendments if the opposition supported a constitutional reform aimed at trimming presidential powers.
Many Ukrainians watched the heated debates in the parliament
But the deal collapsed after the Yushchenko camp said they would consider the constitutional changes only after the electoral amendments were approved.
Addressing a rally in Kiev later on Saturday, Mr Yushchenko said the government tried to force the debate of the constitutional reforms to stall adoption of the electoral changes.
Mr Yushchenko said he was willing to discuss political reform as Mr Kuchma has demanded - but not until after the election.
The president accused the opposition of sabotaging a compromise deal agreed during roundtable discussions last week.
In a statement, Mr Kuchma said the opposition's bickering was "leading to an increase of tensions in the country".
The third round of the Monday talks were expected to be attended by the same mediators - Polish President Aleksander Kwasniewski, EU foreign policy chief Javier Solana and Russia's parliamentary speaker Boris Gryzlov.