KIEV: Russian President Vladimir Putin on Sunday defended the separatist drive in the disputed Crimean Peninsula as in keeping with international law, but Ukraine's prime minister vowed not to relinquish “a single centimetre” of his country's territory.

Over the weekend, the Kremlin beefed up its military presence in Crimea, a part of Ukraine since 1954, and pro-Russia forces keep pushing for a vote in favour of reunification with Moscow in a referendum the local parliament has scheduled for next Sunday.

President Barack Obama has warned that the March 16 vote would violate international law.

But in Moscow, Putin made it clear that he supports the referendum in phone calls with German Chancellor Angela Merkel and British Minister David Cameron.

''The steps taken by the legitimate leadership of Crimea are based on the norms of international law and aim to ensure the legal interests of the population of the peninsula,” said Putin, according to the Kremlin.

Following an extraordinary Sunday meeting of the Ukrainian government, Prime Minister Arseniy Yatsenyuk announced that he will meet with Obama in Washington on Wednesday on a “resolution of the situation in Ukraine,” the Interfax news agency reported. The White House confirmed the meeting.

''Our country and our people are facing the biggest challenges in the history of modern independent Ukraine,” the prime minister said earlier in the day. “Will we be able to deal with these challenges? There should only be one answer to this question and that is: yes.''

In an emotional climate of crisis, Ukraine on Sunday solemnly commemorated the 200th anniversary of the birth of its greatest poet, Taras Shevchenko, a son of peasant serfs who is a national hero and is considered the father of modern Ukrainian literature.

''This is our land,” Yatsenyuk told a crowd gathered at the Kiev statue to Shevchenko.“Our fathers and grandfathers have spilled their blood for this land. And we won't budge a single centimetre from Ukrainian land. Let Russia and its president know this.''

''We're one country, one family and we're here together with our kobzar (bard) Taras,” said acting President Oleksandr Turchynov. Later, Ukrainians in the tens of thousands massed in the Kiev's centre for a multi-faith prayer meeting to display unity and honour Shevchenko.

One of the speakers, former imprisoned Russian tycoon Mikhail Khodorkovsky, almost burst into tears as he implored the crowd to believe not all Russians support their country's recent actions in Ukraine.

''I want you to know there is a completely different Russia,” Khodorkovsky said.

In the eastern city of Luhansk, however, people who gathered in a square to celebrate Shevchenko's birthday were attacked by pro-Russia protesters, and some were beaten up, local media reports said.—AP