Obama Threatens More Sanctions On Russia
The US has imposed sanctions against Russian officials after Crimea's referendum to secede from Ukraine and join Russia.
An executive order by Barack Obama names seven Russian government officials, including top aides to Russian President Vladimir Putin.
The Treasury Department is also imposing sanctions on four Ukrainians, including former President Viktor Yanukovych and two Crimea-based separatist leaders.
Mr Obama said the new sanctions aim to make it clear to the Russians "that there are consequences for their actions" in the Crimean peninsula.
The measures are one of the most comprehensive sets of sanctions against Russia since the end of the Cold War.
But they appeared to do little to dissuade Mr Putin, with the Kremlin announcing that he had signed a decree on Monday recognising Crimea as a "sovereign and independent country".
Earlier, Russian Deputy Prime Minister Dmitry Rogozin, who was named in the US list, suggested the measures would not affect those without assets abroad.
"Comrade Obama, and what will you do with those who have neither accounts nor property abroad? Or didn't you think of that?" he wrote on Twitter.
The announcement in Washington came shortly after the European Union slapped travel bans and asset freezes on 21 people.
The sanctions had been widely expected after Crimea voted overwhelmingly in favour of the split in Sunday's referendum.
Crimea's parliament has declared the region an independent state.
In a phone call after the vote, Mr Obama told Mr Putin that Crimea's vote to join Russia "would never be recognised" by Washington.
And US administration officials say there is some concrete evidence that some ballots for the referendum arrived pre-marked in many cities and "there are massive anomalies in the vote".
The US, European Union and others say it violates the Ukrainian constitution and international law, and took place in the strategic peninsula under duress of Russian military intervention.
Mr Putin says the vote was legal and consistent with the right of self-determination.
The Crimea crisis triggered the worst stand-off between Russia and the US since the end of the Cold War.
At home, Mr Obama has faced accusations from Republicans that he has not shown enough resolve against Mr Putin.
Mr Obama is calling on Russia to pursue a diplomatic de-escalation of the crisis and support the Ukrainian government's plans for political reform.
He called on Russian troops in Crimea to return to their bases and halt advances into Ukrainian territory and military build-ups along Ukraine's borders.
The US has warned that any Russian moves on east and south Ukraine would be a grave escalation requiring additional responses.