International pressure is growing for doing something to stop Syrian President Bashar Assad's crackdown on protesters amid diplomatic confusion and conflicting prescriptions for a solution.

The European Union and the Obama administration toughened sanctions against Assad's government this month but negotiators in published comments acknowledged an ongoing diplomatic stalemate. The United Nations estimates that at least 5,000 people have been killed since the uprising against began in March.

The ultra-conservative Henry Jackson Society in London spelled out arguments it said justified a military intervention in Syria but independent analysts said the actual state of affairs in Syria is far from clear.

Commentator Charles Glass cited reports of heavy arms flows for the anti-Assad forces in Syria but no one seemed to know or divulge their source.

"Someone is fueling violence in Syria with deliveries of weapons," Glass wrote in the London Standard newspaper, citing reports of arms trafficking from Lebanon and Turkey.

He said Western policy on Syria remained unclear. "Before American (and probably British) soldiers are asked to give their lives in another Arab country, they are entitled to ask important questions.

"Is Washington attempting to install a democratic government in Damascus? Or is it seizing the opportunity to bring down Iran's main Arab ally in advance of an American or Israeli attack on Iran?" Glass asked.

He cited reports that private Western security firms that previously worked in Iraq could be active in Syria.

Henry Jackson Society communications director Michael Weiss argued for war and outlined ways in which any international intervention could circumvent the need for U.N. approval.

Both Turkey and the Syrian National Council opposition government-in-exile were well-placed to legitimize the military option, Weiss indicated.

Turkey could plead for self-defense because of growing security risks from across the Syrian border and SNC could call for international assistance against Assad's forces, Weiss said.

He said SNC's OK for a military intervention was required as a precondition. SNC, he said, "must formally accept foreign military intervention as a viable strategy for hastening the end of the Assad regime."

SNC is known to run the Free Syrian Army paramilitary group, made up of defecting Syrian military personnel and other elements.

Glass questioned the Syrian opposition's credentials and cited U.S. support to the opposition going as far back as 2006.

"Washington's support for regime change has escalated in recent months, backed by the region's major Sunni-led states -- Turkey, Jordan, Saudi Arabia and Qatar," Glass said. Assad leads a minority Shiite government in Syria.

"Syrians have legitimate grievances but they should be wary of inviting foreigners with their own agendas to assist them," Glass said.

The Syrian government has blamed terrorists and foreigners for the violence.

Car bombs in Damascus killed at least 40 people Friday as Arab League monitors began their mission to end the violence that has raged since March.

Syrian Deputy Foreign Minister Faisal Mukdad said at least 100 people were injured in the suicide-bomb attacks on two security facilities. There were reports of violence in other towns.

About 30 to 50 observers, headed by league Assistant Secretary-General Samir Saif al-Yazal, would likely make up an initial monitoring mission and work with the Assad regime to decide where the observers would be deployed, al-Jazeera reported.

The observers are in Syria to monitor regime compliance with its pledges to withdraw troops from besieged areas and implement an Arab League peace agreement signed by Syrian officials.

The U.N. Security Council is reviewing a new Russian draft resolution amid Russian warnings that U.N. action can lead to a situation like the NATO-led operation in Libya and exacerbate the crisis.

With army defections on the rise, however, the United Nations warned the prospects for civil war in Syria are growing.

"Will Syria suffer the kind of sectarian bloodbath that has yet to end in Iraq, despite the American pullout?" Glass asked.

"The Iraqi government clearly fears a Syrian conflict spilling across its border and is urging caution," Glass said.