U.S. President Barack Obama and Russian counterpart Vladimir Putin found little common ground during an hour-long phone call to discuss the crisis in Ukraine.
During the call Thursday, the White House says President Obama told Mr. Putin the presence of Russian forces in the Crimean Peninsula is a violation of Ukraine's sovereignty.
It is the first known direct contact between the leaders since Russian military personnel appeared in the Ukrainian territory Saturday, following the ouster of Ukraine's Moscow-friendly leaders.
A Kremlin statement Friday quoted Mr. Putin as saying Ukraine's new Western-backed leaders are illegitimate and are dictating "absolutely illegitimate decisions to the eastern and southeastern regions of Ukraine and Crimea."
While Mr. Putin stressed the "paramount importance" of Russian-American relations, he said "Russia cannot ignore calls for help in this matter and it acts accordingly, in full compliance with international law."
The White House said Mr. Obama proposed several diplomatic solutions to the standoff, which it said address "the interests of Russia, the people of Ukraine and the international community."
As part of the solution, the president called for direct talks between Kyiv and Moscow that would be mediated by the international community. Mr. Obama also called for all Russian forces to return to their bases and for international monitors to ensure the safety of all Ukrainians, including ethnic Russians.
The U.S. statement said Secretary of State John Kerry will continue discussions with Russian Foreign Minister Sergei Lavrov, the Kyiv government and other international partners in the days to come.
Earlier in the day, Mr. Obama signed an executive order authorizing sanctions on those found to have stolen assets of the Ukrainian people or to have violated Ukraine's territorial integrity. The order blocks the transfer from the United States of assets belonging to anyone found to have undermined democratic institutions in Ukraine. The order also includes visa restrictions, but does not name targeted individuals.
The president said a March 16 referendum decreed by pro-Russian Crimean lawmakers on the future of the peninsula violates international law and Ukraine's constitution. He said any discussion about Ukraine's future "must include the legitimate government of Ukraine."
On Capitol Hill, the House of Representatives voted to provide loan guarantees of $1 billion to Ukraine, as the European Union prepares to extend a $15 billion bailout to Kyiv. The measure now goes to the U.S. Senate.
Earlier, the European Union voted to freeze the assets in Europe held by 18 Ukrainians, including ousted president Viktor Yanukovych, former prime minister Mykola Azarov and 16 former ministers, businessmen and security chiefs. Mr. Yanukovych's two sons and Mr. Azarov's son also were targeted.
The EU, facing what its leaders say is the the continent's greatest security challenge since the Balkan wars, also is suspending visa talks with Moscow.