A power struggle between Ukraine's president and prime minister deepened today with both men refusing to back down over a new election and threatening each other with prosecution.
President Viktor Yushchenko has issued a decree to dissolve parliament and stage an election in what is regarded as a final bid to reassert his authority. Prime Minister Viktor Yanukovich has refused to take part in the poll.
The pro-Western president's popularity has slid after accusations he betrayed the promise of the "Orange Revolution" over two years ago to take ex-Soviet Ukraine closer to the West and eventually join the European Union.
He accuses Mr Yanukovich, whom he swept aside in that upheaval, of violating the constitution by poaching members of his team to enlarge the majority in parliament underpinning the government.
Thousands of the prime minister's supporters, many brought by bus from his power base in eastern Ukraine, have taken to the streets, calling for Mr Yushchenko to step down.
Unlike in 2004, gatherings in Kiev's Independence Square were relatively small and low-key.
"I stress one more time that it is obligatory to implement the decree of Ukraine's president. Any refusal to implement it will result in criminal proceedings," Mr Yushchenko told a meeting of Ukraine's Security Council, where he sat next to Mr Yanukovich. "I will not take a single step towards rescinding the decree."
Mr Yanukovich rebuffed the Security Council's approval for the election and said Ukraine should wait for the Constitutional Court to rule on whether parliament's dissolution was legal.
The court said today it had started examining the petition but a ruling could be expected no earlier than a month from now.
"We reject any form of early elections," Mr Yanukovich told a news conference. He urged the president to start talks and asked Austria to mediate to help resolve the crisis.
Polish President Lech Kaczynski offered his services as a mediator - a role his predecessor performed during the 2004 revolution.
European Union foreign policy chief Javier Solana has telephoned the main protagonists in Ukraine's political crisis to appeal for a political solution and restraint. Mr Solana's calls were the first direct EU intervention in the standoff.
The muted EU and Nato response to the crisis reflects disenchantment with Ukraine's progress in reforms two years after the democratic "Orange Revolution".
It may also betray relief among some west European countries opposed to a further eastward enlargement of the bloc.
Mr Solana played an active mediation role in the December 2004 upheaval in Kiev, when mass protests by pro-Western activists led to a court ruling ordering a rerun of a rigged presidential election in which Mr Yushchenko beat Mr Yanukovich.
The latest crisis raises the question of whether Ukraine will return to the Russian sphere of influence or remain on a slower course towards closer ties with the West.