France and Germany yesterday warned Russia of "consequences" if Moscow continued to sow unrest ahead of Ukraine's presidential election this month, on the eve of sovereignty referendums the West fears will split the country.
French President Francois Hollande and German Chancellor Angela Merkel also urged Ukraine's security forces to stop their offensive on rebel-held positions ahead of the planned May 25 election.
The warnings suggest the West may soon move to broaden its sanctions regime to include whole sections of the recession-bound Russian economy.
But the call for the pro-Western government in Kiev to dial back its military action echoes a statement on Wednesday by Russian President Vladimir Putin, who set that as his condition for backing the election.
"If the internationally recognised presidential elections do not take place on May 25, this would destabilise the country further. France and Germany believe that in this case, appropriate consequences should be drawn," indicating stepped-up sanctions, the two leaders said.
Paris and Berlin said that what they called proportionate force should be used to protect people and buildings as Kiev battles to wrest back control of more than a dozen eastern towns and cities held by pro-Russian insurgents.
But they stressed "the Ukrainian security services should refrain from offensive actions before the election". Paris and Berlin also demanded a "visible withdrawal" of Russian troops from the Ukrainian border.
Putin said on Wednesday the estimated 40,000 servicemen had been pulled back, but Nato said there was no sign of that. Ukraine's interim president, Oleksandr Turchynov, said Kiev was "ready for negotiations" with representatives from the region, but "not terrorists whose mission is to destroy the country".
While the diplomatic pressure on Russia intensified, the situation on the ground remained combustible as the southern city of Mariupol observed a day of mourning for up to 21 people killed in clashes on Friday between Ukrainian authorities and pro-Russian separatists.
Meanwhile, preparations were in full swing for the disputed referendums in the two eastern regions of Donetsk and Lugansk, home to 7.3 million of Ukraine's total population of 46 million.
Merkel and Hollande dismissed the referendums as illegal, amid Western fears they will hasten the break-up of Ukraine and could lead to all-out civil war on Europe's fringes.
Voters in today's referendums will first be asked if they support the creation of two independent republics that many see as a prelude to joining Russia.