President Vladimir Putin said Russia and the United States still stood far apart over Ukraine, but the two countries should not sacrifice relations over a disagreement on an individual, albeit very important, international problem.
In a statement issued by the Kremlin on Friday, the Russian leader told US President Barack Obama in a telephone call on Thursday that Ukraine's new leaders, who had come to power in an anti-constitutional coup, had imposed "absolutely illegitimate decisions on the eastern, southeastern and Crimea regions".
On Thursday, parliament in Ukraine's southern Crimea region voted to join Russia and hold a referendum on becoming part of the Russian federation on March 16, moves which pro-Western leaders in Kiev said would violate international law.
"Russia cannot ignore calls for help in this matter and it acts accordingly, in full compliance with the international law," Putin said.
"(He) stressed 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."
In the one-hour call, Obama urged Putin to accept the terms of a potential diplomatic solution to the crisis, which has triggered the worst crisis in US-Russian relations since the end of the Cold War.
Putin has stridently defended Russia's moves in Ukraine, a country he calls "a brotherly nation", saying Moscow was not behind the seizure of Crimea, home of Russia's Black Sea Fleet.
He has denied western accusations that his troops have captured state buildings there, saying the armed men were member of local self-defense units.
He says Russia is willing to cooperate with western powers but any solution to the crisis must be based on an EU-brokered agreement signed on Feb. 21 by ousted leader Viktor Yanukovich, who Putin has said is Ukraine's legitimate president.
Putin said he agreed with Obama that Foreign Minister Sergey Lavrov and US Secretary of State John Kerry should continue "intensive contacts" on Ukraine.