US spy chief: Syria's Assad cannot hold power

"I personally believe it's a question of time before Assad falls, but that's the issue, it could be a long time," Clapper told a Senate intelligence committee hearing. "Protraction of these demonstrations, the opposition continues to be fragmented, but I do not see how he can sustain his rule of Syria."

Meanwhile, British newspaper the Guardian reported that a copy of the draft U.N. resolution demanding Assad step aside tried to address Russian concerns that the vote could open the door to western military intervention.

The draft obtained by the newspaper said the council is "reaffirming its strong commitment to the sovereignty, independence, unity and territorial integrity of Syria, emphasising the need to resolve the current crisis in Syria peacefully, and stressing that nothing in this resolution compels states to resort to the use of force or the threat of force," according to the newspaper.

•  World Blog: Latest violence could signal new phase in Syria conflict

The draft did not entirely exclude the possibility of military action, however, the newspaper reported.

Published at 8:30 a.m. ET: A senior Russian diplomat warned Tuesday that a draft U.N. resolution demanding Syrian President Bashar Assad step aside is a "path to civil war," as Syrian troops crushed pockets of resistance by rebel soldiers on the outskirts of Damascus.

The U.N. Security Council was to meet Tuesday to discuss the draft, backed by Western and some Arab powers. But Russia would likely veto any punitive action.

"The Western draft Security Council resolution on Syria does not lead to a search for compromise," Russia's Deputy Foreign Minister Gennady Gatilov wrote on Twitter. "Pushing this resolution is a path to civil war."

Russia has been one of Assad's strongest backers as he tries to crush an uprising that began nearly 11 months ago. In October, Moscow vetoed the first council attempt to condemn Syria's crackdown and has shown little sign of budging in its opposition.

The draft text of the resolution, seen by The Associated Press, insists there will be no use of foreign forces in the country. It calls on Assad's regime to immediately put "an end to all human rights violations and attacks against those exercising their rights to freedom of expression."

It calls on Assad to delegate his "full authority to his deputy" to allow a national unity government to lead transition to a democratic system. The text, the drafting of which has been led by Morocco, insists it does not compel "states to resort to the use of force, or the threat of force."

U.N. Secretary-General Ban Ki-moon said on Tuesday he hoped the Security Council would reflect international will when it deliberates the resolution.

"I sincerely hope the Security Council will be united and speak in a coherent manner reflecting the wishes of the international community," Ban told reporters in the Jordanian capital Amman. "This is crucially important."

China, which like Russia has a veto in the council, also has reservations about the draft. Russia and China vetoed a European-drafted resolution in October that condemned Syria and threatened it with sanctions.

"I don't think we can go on like this," Ban said.

Syria's crackdown on protesters and anti-government fighters had gone on despite a now-suspended Arab League monitoring mission and action was needed to stop the bloodshed, he said.

"Even with the monitoring missions having been there, more than a few hundred have been killed ... every day tens of people are killed ... this should stop immediately," Ban said. "It is crucially important for the Security Council to act on this."

Escalating violence
Meanwhile Tuesday, government troops were deploying in "massive numbers" to the suburbs of Damascus, the U.K.-based Syrian Observatory for Human Rights told NBC News. The group said at least 11 people had been killed as of Tuesday morning.

• Story: Gunfire 'everywhere': Street battles rage in Damascus suburbs

The Observatory, which supports the Free Syrian Army, said government forces were targeting civilians who were aiding defectors, NBC reported.

Fighting has escalated in the past several days with at least 100 people killed on Monday alone.

The office of U.N. High Commissioner for Human Rights Navi Pillay voiced alarm on Tuesday at the escalating violence and called on Syrian authorities to "stop the killing of civilians" while also urging opposition forces to show restraint.

"It does look like there's a very dangerous and alarming escalation taking place including right in the suburbs of Damascus," U.N. human rights spokesman Rupert Colville told a news briefing in Geneva.

"So once again we urge the Syrian authorities to stop the killing of civilians in Syria. And we also urge the opposition fighters to take extreme caution too and ensure that there is no more unnecessary killing," he said.

More than 5,000 people have been killed in the uprising as of mid-December, according to Pillay's office.

Despite "high rates of casualties" since then, it has been impossible to verify incidents and lists of victims compiled by five or six human rights groups on the ground, Colville said.