Western leaders tell Russia to back off amid flurry of diplomatic activity and rising tensions in flashpoint region of Crimea.

The White House warned Russia to keep its troops out of Ukraine, amid fears that Moscow may step in with military force following the overthrow of the President, its ally.

Tensions also mounted in Crimea, in Ukraine's southeast, where pro-Russian politicians are organising rallies and forming protest units demanding separation from Kiev. The region is now seen as a potential flashpoint because of its deep strategic significance to Moscow.

US President Barack Obama's National Security Adviser, Susan Rice, said it would be a "grave mistake" for Russian President Vladimir Putin to send soldiers into Ukraine to restore a friendly government after the upheaval. Nobody would benefit if Ukraine were to split apart, she said. "It's in nobody's interest to see violence return and the situation escalate."

Her warning to the Kremlin followed concerns over renewed tumult in Ukraine if eastern regions of the vast country side with Russia against the overthrow of Viktor Yanukovych.


US Secretary of State John Kerry, in a call to his Russian counterpart Foreign Minister Sergei Lavrov, underscored Washington's expectation that "Ukraine's sovereignty, territorial integrity and democratic freedom of choice will be respected by all states".

Fears that Ukraine could splinter are spurring intense activity in the West to keep the country together, while also seeking to placate Russia over Kiev's tilt away from Moscow. EU foreign policy chief Catherine Ashton is to begin a two-day visit to Kiev today to speak with Ukraine's interim leaders. Ashton, German Chancellor Angela Merkel and French President Francois Hollande all stressed separately that Ukraine must forge a political solution that guarantees its "unity".

Both Washington and EU powers vowed to drum up aid that could pull Ukraine out of a crisis, sparked in November when Yanukovych spurned a historic EU trade deal and later secured a US$15 billion ($18.1 billion) bailout pledge for the struggling nation from Russia. Moscow once again warned that delivery of its huge bailout package was on hold. In a move highlighting Russia's displeasure, it recalled its ambassador to Kiev for "consultations". The Russian Foreign Ministry also said Lavrov had flatly told Kerry that Russia strongly condemned "the seizure of power" by the opposition.

Trying to defuse Russian anger, Merkel held a phone conversation with Putin in which "both agreed Ukraine must quickly get a government capable of acting and its territorial integrity must be preserved", according to a German government spokesman.

The queue of politicians warning Russia to back off is a measure of how dangerous the situation is considered to be. But many analysts believe the country's faultline has been overstated, ignoring a widespread Ukrainian identity, while Russia has no desire to blunder into a confrontation. Many analysts say domestic discontent played a large role in the upheaval with anger at Yanukovych's corrupt crony capitalism, the lack of rule of law and an overcentralised constitution felt all across the country.

The Kremlin is likely to have been as surprised as those in Western capitals by the speed of events in Ukraine. Analysts believe it will wait to see the makeup of any new government. A strongly anti-Russian government spouting anti-Russian rhetoric will force it to act. Moscow's strongest cards may be financial rather than military, including gas contracts and the agreed bailout.

Rice said it would be a mistake for Putin to view the tumult as a Cold War battle between the East and West. "That's a pretty dated perspective that doesn't reflect where the people of Ukraine are coming from. This is not about the US and Russia." She said the country need not be torn apart on a cultural faultline between pro-Russian and pro-Europe Ukrainians.

Lilit Gevorgyan, a Russia analyst at IHS Jane's Insight, said: "If there's turmoil and real talk of the breakup of Ukraine, the Russians will be interested in securing" Crimea's Sevastopol port. "Strategically, symbolically and historically, it's important for the Russians."

She said: "There are many Russians who believe it was [former Soviet leader Nikita] Khrushchev, who was an ethnic Ukrainian, who decided to give [Sevastopol] to Ukraine, and still believe it is unfair. If it had been part of Russia, it would have provided a deepwater port for its Black Sea fleet, whereas Russia now has to pay a lease until 2042."

In a recent opinion poll, 56 per cent of Russians said they viewed Crimea as a Russian territory, a far higher proportion than felt a claim on Chechnya. But Gevorgyan said the Crimean population was extremely diverse, and might prove difficult for Russian nationalists to manipulate. In particular, the region's significant population of Muslim Tartars, who suffered persecution and mass deportation under Stalin, have little desire to join Russia. "It's a patchwork of different identities and I'm not sure it will be easy to manipulate. It has never been either truly Russian or truly Ukrainian."