Syrians from Sheikh Maskeen region, southern Syria, head to Deraa to support protesters there in March. (REUTERS/Khaled al-Hariri)

“Despite a ferocious and desperate attempt by Bashar al-Assad to beat the Syrian people into silence this week, thousands of courageous Syrians have returned to the streets in towns and cities across the country today to demand their rights,” Sens. John McCain (R-Ariz.), Joe Lieberman (I-Conn.) and Marco Rubio (R-Fla.) said in a joint statement Friday.

“At this critical moment, we believe President Obama’s leadership is vitally important,” they added. “We urge the President, together with our other allies around the world, to join the call of the protesters echoing across Syria today -- that Bashar al-Assad has lost the legitimacy to lead, and that it is time for him and his regime to go.”

The three senators said that Obama “should expand sanctions immediately against those officials responsible for the dramatically expanded campaign of repression and violence in Syria, including Bashar al Assad personally.”

The senators’ call for further action follows the Obama administration’s imposition of sanctions last month on the Syrian intelligence service as well as three Syrian officials. Human rights groups have estimated that as many as 700 people have been killed and 10,000 detained since the anti-government protests began in March.

Earlier this week, a bipartisan group of 16 senators including McCain, Lieberman and Rubio introduced a resolution condemning the crackdown by the Assad government and calling on Obama to expand sanctions against the Syrian president as well as other officials. The resolution has yet to be taken up by the Senate; the trio of senators on Friday urged their colleagues to pass the measure, adding that the move would “send a strong bipartisan message” that the U.S. will not tolerate Syrian oppression.

At Wednesday’s news conference announcing the resolution, Lieberman and McCain said they did not believe the U.S. should intervene militarily in Syria at the moment, noting that the Syrian opposition has not yet asked for U.S. support.

Secretary of State Hillary Rodham Clinton on Thursday suggested that the administration is considering a tougher response to Assad, The Post’s Liz Sly reports.

“The recent events in Syria make clear that the country cannot return to the way it was before,” Clinton said.