Qatar has made a fresh call for an Arab force to end bloodshed in Syria if current diplomatic efforts by international peace envoy Lakhdar Brahimi fail, according to the Doha-based al Jazeera television.

Brahimi is trying to build on an agreement reached in Geneva on June 30 calling for a transitional period in Syria. But differences between Russia and the United States over the future of President Bashar al-Assad continue to block a deal to end 21 months of violence that has killed more than 60,000 Syrians.

"Arabs must think seriously about sending forces to ensure security in Syria if diplomatic efforts fail to resolve the crisis," Qatar's Prime Minister and Foreign Minister, Sheikh Hamad bin Jassim al-Thani, said in remarks broadcast by al Jazeera television.

"It is not a question of intervention in Syria in favour of one party against the other, but rather a force to preserve security," Sheikh Hamad, who also heads an Arab League committee on Syria, said.

The Gulf Arab state, a supporter of rebels seeking to overthrow Assad, made a similar proposal in September.

In a speech to the UN General Assembly, Qatari Emir Sheikh Hamad bin Khalifa al-Thani said Arab states should intervene in Syria given the UN Security Council's failure to stop the civil war.

Apart from Qatar, Saudi Arabia and Turkey strongly support the mainly Sunni Muslim Syrian rebels, while Shi'ite Iran backs Assad, whose Alawite minority is an offshoot of Shi'ite Islam.

Russia on Saturday voiced support for Brahimi's efforts but insisted Assad's exit cannot be a precondition for a deal to end the country's conflict.

Brahimi indicated the issue of Assad, whom the United States, European powers and Gulf-led Arab states insist must step down to end the war, was a sticking point at a meeting on Friday with envoys from Russia and the United States .

"We support this effort," said Sheikh Hamad, refering to Brahimi's peace initiative. "But until when? We cannot wait forever on this issue."