By Li Hongmei

The U.S. and European Union put Russian President Vladimir Putin on notice that they will be united on imposing sanctions if he's unwilling to defuse the Ukraine crisis and pursue a negotiated solution.

As Crimean separatists backed by Russian forces pushed to split from Ukraine, the U.S. banned visas for Russian officials and others it said were complicit in violating the sovereignty of the ex-Soviet state of 45 million. U.S. President Barack Obama signed an order authorizing financial sanctions, while EU leaders halted trade and visa talks with Russia and threatened punitive economic measures in what's become the worst rift between Russia and the West since the Cold War era.

Despite signs of divisions among EU leaders, Obama said today he's confident that "we are moving forward together" to press Russia toward the "path of de-escalation."

The U.S. and its allies will keep increasing pressure "to impose a cost on Russia and those responsible for the situation in Crimea," he said at the White House. Implementation will be flexible "based on Russia's actions," he said.

Obama told Putin in an hour-long phone call today that Russia's actions have violated Ukraine's territorial integrity and brought on the penalties unveiled by the U.S. and EU, according to a White House statement. The standoff can be resolved diplomatically, through talks between Russia and Ukraine's government, Obama told Putin, the White House said.

Putin and Obama hold differing views on the crisis, though U.S.-Russia relations shouldn't be sacrificed, the Kremlin said in an e-mailed statement on the leaders' conversation.

The EU leaders agreed to make preparations for sanctions, as well as accelerate the timetable to draw Ukraine closer to the 28-nation bloc, EU President Herman Van Rompuy said. If Russia doesn't back down, European nations "will decide on additional measures, such as travel bans, asset freezes and the cancellation of the EU-Russia summit," he told reporters.

Obama, in the executive order, authorized Treasury Secretary Jacob J. Lew to take steps that could include freezing assets or blocking American companies or individuals from doing business with Russians, Ukrainians or others deemed a threat to Ukraine's security.

The Treasury Department is redoubling efforts to prevent illegally acquired Ukrainian assets from leaving the country, concerned that such transfers might destabilize the global financial system, said a department official who spoke by phone today under the condition of not being further identified.

The U.S. has held back on implementing such sanctions to give Putin time to consider a western proposal, Secretary of State John Kerry said. His remarks reflect uncertainty about how Putin will respond to such threats.

Economic Leverage

Anders Aslund, a senior fellow at the Peterson Institute for International Economics in Washington, said the Europeans have greater economic leverage than the U.S. does -- and greater financial stakes given their own trade ties to Russia.

"Economic pressure essentially depends on Europeans taking strong actions, because Europe receives nearly half of Russia's exports, while the United States only takes 3 percent of Russia's exports," he said in an e-mail.

Europe depends on Russia for almost a third of its natural gas needs, including gas sent via pipelines through Ukraine.

With Ukraine's problems magnified by the threat of default, the U.S. and Europeans also are taking steps to aid the new government.

The U.S. House of Representatives voted 385-23 for a bill to allow $1 billion in loan guarantees for Ukraine sought by the Obama administration.

The European Commission, the EU's executive arm, yesterday outlined a wide-ranging Ukraine aid package worth 11 billion euros (about $15 billion) in loans and grants over the next couple of years, tied to the Kiev government striking a deal with the International Monetary Fund.

Rejoining Russia

In contrast, lawmakers in Crimea voted in a non-binding measure to become part of Russia if voters agree in a referendum March 16. They also asked Putin and the parliament in Moscow to begin crafting procedures to make the province part of the Russian Federation, the state-run Crimean Information Agency reported.

Western leaders, including Obama and British Prime Minister David Cameron, said today that such a referendum would be unconstitutional and illegal.

Former Ukrainian Prime Minister Yulia Tymoshenko, who was jailed under Yanukovych, rejected a referendum as illegal and said Russian withdrawal is the "point of departure" for any negotiations.

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