US Senator John McCain has lambasted Barack Obama during a public speech on Ukraine crisis.
During the public address to the American Israel Public Affairs Committee, McCain said Obama's foreign policy was ineffective.
The senator then called on Obama's administration to enact sanctions against Russia and prevent it from attacking Crimea, the Washington Post reported.
"Why do we care? Because this is the ultimate result of a feckless foreign policy in which nobody believes in America's strength anymore," McCain said.
McCain, who lost to Obama in the 2008 presidential elections, accused the president of underestimating Putin's goals in the region.
"The president of the United States believes the Cold War is over; fine — it's over. But Putin doesn't believe it's over".
McCain also cited remarks Obama made at a summit in South Korea in 2012, in which he was caught on an open microphone telling Prime Minister of Russia Dmitry Medvedev that he would be more flexible towards Russia after his re-election.
President Barack Obama held an emergency meeting with his national security advisers to discuss measures to isolate Russia on the international stage following its military incursion into Crimea.
United States Ambassador Samantha Power said military action in Crimea could have devastating consequences.
"Russian military action is not a human rights protection mission," Power said. "It is a violation of international law."
The US State Department is preparing to impose sanctions on Russia including sanctions on Russian banks and freezing the assets of Russian public institutions and private investors, Reuters reported.
However, the report added that the US is hesitant about acting alone and wants the European Union to adopt a tough line against Moscow.
"The most important thing is for us – the United States -- to make sure that we don't go off without the European community. Their interests are really paramount if we are going to do sanctions of some kind. We have to have them on board with us," Senate majority leader Harry Reid said.