As East-West diplomatic tensions simmer over Ukraine, the White House says President Barack Obama told Russian counterpart Vladimir Putin Thursday that Moscow's actions in Ukraine violate that country's sovereignty.
A White House statement said the two leaders spoke for an hour, during which Mr. Obama detailed actions taken by Washington and its allies in response to the presence of Russian forces in the Crimean peninsula.
It is the first known direct contact between the leaders since Russian military personnel appeared in the Ukrainian territory Saturday.
The statement 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 statement said U.S. 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.