Obama gives Ukraine full backing as stand-off hardens

The East-West split re-opened by the crisis in Ukraine hardened Wednesday when President Barack Obama threw Washington's weight firmly behind Ukraine in its stand-off with Moscow.

Obama welcomed Kiev's interim premier Arseniy Yatsenyuk to the White House and stood by his side as both leaders sternly warned Russia that Ukraine would not surrender its sovereignty.

Obama repeated that Moscow would face unspecified "costs" if Russian President Vladimir Putin does not back down, and rejected a bid to hold what he called a "slapdash" referendum in Crimea.

"There's another path available and we hope President Putin is willing to seize that path," Obama told White House reporters, sitting alongside Yatsenyuk after their talks the Oval Office.

"But if he does not, I'm very confident that the international community will stand firmly behind the Ukrainian government."

Yatsenyuk thanked Washington for its support and declared: "We fight for our freedom. We fight for our independence. We fight for our sovereignty. And we will never surrender."

Breakaway leaders on Ukraine's Crimean Peninsula, backed by Putin, plan to hold a referendum on Sunday to split from Kiev and come under Moscow's wing.

Russian troops backed by ad hoc local militias secured the territory in the chaotic days last month after Ukraine's former pro-Kremlin leader Viktor Yanukovych was overthrown by a street revolt.

Obama said he hopes the crisis can be resolved through diplomacy, but Ukraine and the West do not recognize the referendum and Moscow does not recognize the Kiev government.

"We have been very clear that we consider the Russian incursion into Crimea outside of its bases to be a violation of international law," Obama said, underlining the depth of the divide.

"And we have been very firm in saying that we will stand with Ukraine and the Ukrainian people in ensuring that that territorial integrity and sovereignty is maintained."

Yatsenyuk said he was "ready and open" for talks with Russia, but warned: "We want to be very clear that Ukraine is and will be a part of the Western world."

During his trip to Washington, Yatsenyuk also plans to try to iron out details of a $35 billion (25-billion-euro) aid package he says his nation's teetering economy needs to stay afloat over the coming two years.

- G7 warns Russia on referendum -

Ukraine has declared it will not recognize Crimea's referendum, and has heavyweight support from the United States and European Union, but admits it would be powerless to intervene militarily.

Putin's diplomatic isolation intensified when the G7 industrialized nations urged Russia "to cease all efforts to change the status of Crimea contrary to Ukrainian law and in violation of international law."

"The annexation of Crimea could have grave implications for the legal order that protects the unity and sovereignty of all states," said a joint statement from the G7 powers.

EU foreign ministers are to discuss punitive measures against senior Russian officials at a meeting on Monday.

European leaders will then meet at a March 20 to 21 summit to witness the signing of what German Chancellor Angela Merkel said would be an historic EU-Ukraine association agreement.

It was Yanukovych's refusal to sign the deal in November -- he chose instead to seek closer economic ties with Moscow -- that sparked the deadly protests that eventually ended his rule.

Washington said Moscow could still avoid sanctions if it softened its stance on Crimea during talks in London on Friday between US Secretary of State John Kerry and Foreign Minister Sergei Lavrov.

Russia's first military involvement in a neighboring country since its brief 2008 war with Georgia has sparked an explosive security crisis and exposed previous rifts between Western allies over ways to deal with Putin's efforts to rebuild vestiges of the Soviet Union.

Washington has already imposed travel bans and asset freezes on Russians held responsible for violating the territorial integrity of the culturally splintered nation of 46 million people.

But the European Union -- its financial and energy sectors much more dependent on Russia than those of the United States -- only threatened tougher measures after taking the lighter step of suspending free travel and broad economic treaty talks.

Yet international opposition has done little to slow Russia's attempt to redraw Europe's post-war borders by absorbing a region that was handed to Ukraine when it was still a Soviet republic in 1954.

On March 21, Russian lawmakers will debate simplifying the procedure under which Moscow can annex a part of another country that proclaims independence -- as Crimean lawmakers did Tuesday.

The self-declared leaders of Crimea, who are holding the referendum, have said they expect an overwhelming "yes" vote in the predominantly ethnic Russian region in favor of joining Kremlin rule.

But the leader of Crimea's Muslim Tatars -- deported en masse by Stalin in 1944 and now representing just 12 percent of the local population -- has already called for a boycott of the vote.

Crimean Tatar leader Mustafa Dzhemilev told Ukraine's Channel 5 television that he spoke by telephone with Putin on Wednesday and "expressed doubts" about the legitimacy of the referendum.