WASHINGTON (MarketWatch) -- President Barack Obama on Friday told the leaders of the four largest European economies that the U.S. is prepared to impose additional sanctions on Russia. In a conference call from South Korea with French President Francois Hollande, German Chancellor Angela Merkel, Italian Prime Minister Matteo Renzi and U.K. Prime Minister David Cameron, Obama said the targeted sanctions would be a response to "Russia's latest actions" in Ukraine, according to a summary of the conversation released by the White House. "The leaders agreed to work closely together, and through the Group of 7 and European Union, to coordinate additional steps to impose costs on Russia," the statement said. The five leaders agreed that despite the agreement reached in Geneva last week Russia had "in fact continued to escalate the situation through its increasingly concerning rhetoric and threatening military exercises on Ukraine's border."