With the president expected to make a key speech to the Muslim world next week, the Obama administration is facing growing pressure from U.S. lawmakers to more directly confront the regime of Syrian President Bashar Assad in the face of mass killings and arrests of his people.

Syria, which is one of only four countries that has been designated by the U.S. State Department as a state sponsor of terrorism, had seemed to be gaining favor with the Obama administration until the protests. President Obama's reward to Syria was the sending of a new ambassador to Damascus, the first time that had happened since the Bush administration withdrew its ambassador in 2005.

On Wednesday, a bipartisan group of U.S. senators, including Joe Lieberman, I-Conn., and John McCain, R-Ariz., put further pressure on the administration by introducing a Sense of the Senate resolution calling for tougher U.S. action against the Assad regime.

Lieberman, speaking at a news conference on the measure, called on Obama to withdraw the U.S. ambassador to Syria, Robert Ford, and expand the unilateral sanctions placed on Syrian officials a week ago to include Bashar Assad.

Assad was "directing everything that's happening in Syria today," Lieberman said, and McCain accused Assad of having "American blood" on his hands for allowing suicide bombers to cross into Iraq and attack U.S. military personnel.

McCain said it was unfortunate that "many in the administration and in the Congress felt that he was someone we could 'do business with' and that he was 'a Reformer.'" McCain said he and others rejected this.

"It's time for the president of the United States to speak up forcefully and frequently," McCain said.

White House Press Secretary Jay Carney, when asked at Wednesday's press briefing why there have been no calls for Assad to step down, would only say that it was up to the people of the region to decide who their leader should be.

Carney said the administration had been "increasing pressure" on Syria, noting last week's targeted sanctions. "It has been made abundantly clear to the Syrian government that its security crackdown will not restore stability and will not stop the demands for change in Syria," Carney said.

Ammar Abdulhamid, a leading Syrian dissident who lives in the U.S., told Fox News that the administration's initial response "was too tentative" and based on a mistaken belief that Assad was still interested in reform, but Abdulhamid thinks the administration's position has gradually changed, becoming "more critical."

He welcomed the recent sanctions imposed on key figures of the Syrian regime, and he said that he's hoping that the U.S. also imposes sanctions against Assad and calls for him to go or face prosecution at the International Criminal Court.

Others foreign policy analysts were not as supportive, angered by the way the administration has let other nations take the lead, as was the case of the recent failed press statement at the United Nations that was sponsored by the Western European members of the council, France, Germany, Britain and Portugal.

"U.S. policy during the Syrian crisis is yet another example of the Obama administrations leading from behind approach, whereby Washington lets American allies take the lead while remaining in the shadows," Nile Gardiner of the conservative Heritage Foundation told Fox News. "This is hardly a strong projection of American global leadership at a time when many on Capitol Hill are questioning President Obama's overall Middle East strategy, which appears to be non-existent."

During Wednesday's news conference, Lieberman said it was thought that as many as 10,000 Syrians had been arbitrarily arrested by the Assad regime, and while human rights groups say the number of dead has risen to over 800, Lieberman urged the president to speak out.

"A statement by the president would mean everything to the people of Syria, and also it would send a very threatening message to Assad," Lieberman said.

Meanwhile, human rights activist Abdulhamid is urging Obama not to forget Syria during his upcoming speech to the Muslim world. He urges the president to tell the world that Assad must step down show the world the U.S. is on "the side of the people" who have been fighting for reforms in the region -- not abandon support for the American values of democracy and freedom.