Syria's splintered opposition factions have begun talks in Qatar on forging a common front for their war against the army of President Bashar al-Assad.

It is the first concerted attempt to meld opposition groups based abroad and align them with rebels fighting in Syria, to help end a 19-month-old conflict that has killed more than 32,000 people and devastated swathes of the major Arab country.

The war threatens to widen into a regional sectarian conflagration.

Tensions between Islamists and secularists as well as between those inside Syria and opposition figures based abroad have thwarted prior attempts to forge a united opposition and analysts sounded a note of caution about the five-day talks.

One Qatar-based security analyst, who asked not to be named, said: "No one was expecting anything to be delivered despite the heavy Qatari hand on this. The Syrian National Council is just too divided. We are likely only looking at a small movement forward."

Sunni Qatar along with Saudi Arabia and Turkey are backing the mainly Sunni rebels, while Shia Iran supports Assad.

The talks in Doha are intended to win greater international support for the rebels and crucial arms supplies.

The US called last week for an overhaul of the opposition's leadership, saying it was time to move beyond the SNC and bring in those "in the front lines fighting and dying".

Secretary of State Hillary Clinton said the meeting in Qatar would be an opportunity to establish a credible opposition.

Car bomb

Earlier today, a car bomb has exploded near a major hotel in the Syrian capital of Damascus, wounding several people, a pro-government television station reported.

The powerful blast shook the Dama Rose hotel and shattered much of its glass, Ikhbariyeh TV reported. The hotel was in the past used by UN observers visiting Syria.

The site of the blast is 500 metres from the army chief-of-staff's building.

The report said the bomb was planted under a car parked in an outdoor lot near the government Labour Union building.

The union chief, Mohammad Azouz, told The Associated Press that at least 12 people - all syndicate members - were wounded by shattered glass and two of them are in a critical condition.