British Foreign Secretary William Hague said on Monday he would visit Ukraine "shortly" and said the revolt-hit country needed urgent financial aid to prop up its economy.

Hague said his Russian counterpart Sergei Lavrov made no mention of military intervention when they spoke by phone Monday, and urged cooperation between the EU and Moscow.

"Ukraine's financial situation is very serious, and without outside assistance may not be sustainable," Hague said in a statement to parliament.

Hague said he would travel to Washington later Monday for talks with US Secretary of State John Kerry and with the International Monetary Fund.

He said the IMF was "best placed" to provide immediate financial and technical support, but stressed that aid would be dependent on economic and political reforms.

Hague noted that European Union foreign affairs chief Catherine Ashton was now in Kiev, "and I will visit shortly", he added.

Ukraine's new masters called on the West on Monday to organise a financial rescue urgently, saying they needed $35 billion to stave off default, while jilted Russia threatened economic punishment.

But Hague said it would be a "mistake" to see Ukraine as "a competition between East and West".

Asked if Lavrov had given any guarantees that Russia, whose Black Sea fleet is based in the Ukrainian region of Crimea, would not take military action, Hague replied: "Mr Lavrov did not raise the issue of military intervention in Ukraine."

"Any notion of this kind is manifestly not in the interests of Russia as well as not in the interests of Ukraine," Hague added.