Russia and the US are still stuck in a stalemate on Ukraine but relations between the two countries should not be sacrificed because of their differences, Vladimir Putin has said after a phone call with Barack Obama.
President Putin's remarks were carried in a Kremlin statement issued on Friday, following the Thursday night telephone call with President Obama, the Reuters news agency reported.
"The discussion revealed the differences in the approaches and assessments of the crisis and current situation," the statement said.
During the one-hour call the US leader urged his Russian counterpart to engage with diplomatic efforts to defuse a crisis that began with anti-government protests in November and this week escalated with a threat of secession in the strategically-important peninsula of Crimea after armed men seized government buildings and military installations.
On Thursday, Crimea's parliament voted unanimously in favour of joining the Russian Federation. A referendum, asking whether the peninsula should retain ties with Kiev or join the federation, is due to take place on March 16.
On Friday, a Ukrainian border guard official reported that 30,000 Russian troops were in Crimea, trumping earlier figures of 11,000 given by the region's leader, Sergei Aksyonov.
The official told the Reuters news agency that the figure was an estimate and included both troops that had arrived last week and those in Russia's Black Sea Fleet based in Sevastopol.
Under a Russia-Ukraine agreement signed in 2010, Russia can have a maximum of 25,000 troops in Crimea.
Moscow has repeatedly denied sending more troops to Crimea, but says it need to protect its interests and people in the peninsular.
That point was reiterated in the Putin statement on Friday: "Russia cannot ignore calls for help in this matter and it acts accordingly, in full compliance with the international law."
The statement added the "paramount importance of Russian-American relations to ensure stability and security in the world. These relations should not be sacrificed for individual differences, albeit very important ones, over international problems."
The Putin-Obama call was the second in six days.
Earlier on Thursday, Obama issued an executive order authorising sanctions against "individuals and entities responsible for activities undermining democratic processes or institutions in Ukraine."
'Unusual and extraordinary'
Obama called Russia's involvement in Crimea "an unusual and extraordinary threat to the national security and foreign policy of the United States".
During the call with Putin, Obama outlined the terms of a compromise - what US diplomats are calling an "off-ramp" settlement - that his officials are promoting.
Under the terms of the deal, Russia would withdraw troops from bases in Crimea, allow international monitors in to ensure the rights of ethnic Russians are respected and agree to direct talks with Ukraine officials.
Chris Bellamy, professor of maritime security at the Greenwich Maritime Institute, told Al Jazeera it was possible but unlikely that Ukraine would lose Crimea.
"Crimea has only been part of Ukraine since 1954. Fifty percent of its population is Russian, 24 percent is Ukrainian and 12 percent are Crimean Tatar...there’s very much a Russian majority," he said.
"But I don’t think the world community likes to break up countries very much. I think giving Crimea back to Russia, while it’s an option, it’s not likely."