KIEV - Ukraine sought urgent Western backing on Monday after Russian President Vladimir Putin insisted that Crimea had the right to join his country even while hinting at a readiness for dialogue.

The pro-European team in Kiev that rode the wave of three months of deadly protests to topple a Kremlin-backed regime is running against the clock to preserve the territorial integrity of the culturally splintered nation of 46 million.

The self-declared leadership on the predominantly ethnic Russian peninsula of Crimea has proclaimed independence from Kiev and set a March 16 referendum on switching over to Kremlin rule.

The decision has been condemned by Western powers who are also furious at Moscow’s seizure of Crimea in a lightning but bloodless operation that began days after the February 22 fall and subsequent escape to Russia of president Viktor Yanukovych.

German Chancellor Angela Merkel - whose cautious approach to imposing sanctions on Russia has clashed with the more hawkish positions of Eastern European nations and the United States - bluntly told Putin on Sunday that the Crimean referendum was “illegal”.

The most explosive East-West crisis since the Cold War was stoked further when the Kremlin said Putin told both Merkel and British Prime Minister David Cameron that he fully recognised the actions of the Crimean leaders - in power since an end of February seizure of the local parliament and government by pro-Kremlin gunmen. The Kremlin said Putin stressed “the steps undertaken by the legitimate authorities of Crimea are based on the norms of international law” - a comment hinting strongly that the Kremlin was ready to annex Crimea after handing the peninsula as a “gift” to Ukraine when it was a part of the Soviet empire in 1954.

Meanwhile, Ukraine's Crimea region has invited the Organization for Security and Cooperation in Europe (OSCE) to send a mission to observe Sunday's referendum on joining Russia, Russia's RIA news agency said on Monday.

It said the invitation had been issued to the Vienna-based security and human rights organisation by the region's pro-Russian parliament. But later in the day, a OSCE spokeswoman said Crimea could not invite observers as the region was not a full-fledged state and therefore not a member of the 57-member organisation. "As far as we know, Crimea is not a participating state of the OSCE, so it would be sort of hard for them to invite us," she said. She also said that Ukraine, which is an OSCE member, sent no invitation and that the organisation "respects the full territorial integrity and sovereignty of Ukraine". For the past week, OSCE military observers have been unable to enter Crimea, which is controlled by Russian forces. On Monday, Sergei Aksyonov, Crimea's newly appointed Prime Minister contested by central authorities in Kiev, said that the pro-Russian authorities in the region "have cordially asked" OSCE observers to leave.

Ukraine, meanwhile, has asked the Council of Europe human rights watchdog to help investigate the clashes that led to President Viktor Yanukovich's overthrow and to monitor minorities in Crimea. Ukrainian Prime Minister Arseny Yatseniuk will address the United Nations Security Council about the situation in Crimea on Thursday, Interfax Ukraine news agency quoted him as saying on Monday. Interfax also quoted him as telling reporters that he believed Russia, whose forces are in control of Ukraine's Crimea peninsula, sought to "undermine the foundations of global security and revise the outcome of World War Two."