KIEV, Ukraine — 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 centimeter” 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 favor of reunification with Moscow in a referendum the local parliament has scheduled for next Sunday.

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

Following an extraordinary Sunday meeting of the Ukrainian government, Prime Minister Arseniy Yatsenyuk announced 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.

In an emotional climate of crisis, Ukraine on Sunday solemnly commemorated the 200th anniversary of the birth of its greatest poet, Taras Shevchenko, who is a national hero.

“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 centimeter from Ukrainian land. Let Russia and its president know this.”