France, Italy, Spain and the Netherlands decided to bring back their envoys for consultations, joining Britain and Belgium to protest the regime's relentless opposition crackdown. Paris denounced the "worsening repression'' while Rome voiced the "firm condemnation and disgust of the Italian government for the unacceptable violence perpetrated by the regime in Damascus against the civilian population''.

The pan-Arab bloc deployed an observer mission to Syria in December to oversee a November plan to end bloodshed that has now lasted almost 11 months.

But the mission, widely criticised as ineffective, was suspended in late January after its chief said the violence had reached a new pitch of intensity despite its presence on the ground.

The 22-member League has since put forward a new plan for Assad to hand his powers to Vice President Faruq al-Shara and for the formation of a national unity government to oversee the preparation of democratic elections.

Shara, a veteran regime diplomat with a career that stretches back to the rule of Assad's late father president Hafez al-Assad, attended the talks with Lavrov, the official SANA news agency said.

"President Assad said that Syria from the start has welcomed any efforts toward a solution to the Syrian crisis and is committed to the Arab League plan that was decided on November 2, 2011," the news agency said.

After Tuesday's talks, Lavrov said he believed Damascus had heard Moscow's message. "We have every reason to believe that the signal that we've brought here to move along in a more active manner along all directions has been heard," he said.

Lavrov confirms Syria was pressing ahead with the reform program which Assad promised in speeches last year and would soon announce the timetable for a referendum on a new constitution to replace the current one that enshrines the dominance of his Baath party. SANA said Assad would receive the text drawn up by an appointed panel on Wednesday.

US State Department spokeswoman Victoria Nuland voiced scepticism over Assad's promises.

"You can understand that the international community as a whole would be pretty sceptical of, instead of focusing on ending the violence, what we seem to have is a re-upping of this same offer that Assad has been making for months and months and months," she told reporters in Washington.

Lavrov adds Assad was also ready for dialogue with all parties.

"Today we've received confirmation of President Assad's readiness to facilitate this work," he said.

But on the ground, there was no let-up in the regime's crackdown on protest hubs around the country, particularly the central city of Homs, Syria's third-largest.

Tanks and artillery pounded Homs for a fourth straight day, killing at least 15 civilians, according to activists, as the interior ministry vowed no let-up in the onslaught against "terrorist groups".

"Operations to hunt down terrorist groups will continue until security and order are re-established in all neighbourhoods of Homs and its environs," pledged an interior ministry statement carried by SANA.

Abu Rami, an activist in the city reached by reporters by telephone from Beirut, said shelling and rocket fire continued through Monday night and into Tuesday.

"There are about four blasts every five minutes," he said. "The humanitarian situation is dire. No one can move around."

At least nine civilians, including a woman, and four soldiers were killed as the army attempted to storm the Khaldiyeh neighbourhood of the city, the Syrian Observatory for Human Rights said.

Another six civilians were killed in the Baba Amr district, the Britain-based watchdog said, adding that a further seven civilians and four security service agents were killed elsewhere in Syria on Tuesday.

Shooting thought to be from outgunned rebels fighters echoed across Baba Amr in response to the artillery barrage from besieging troops.

U.S. Senator John McCain, the Republican candidate in the 2008 election won by President Barack Obama, said it was time for Washington to think about arming the rebels. "We should start considering all options, including arming the opposition. The blood-letting has got to stop," he said.

Human rights groups say more than 6,000 people have been killed since the outbreak of the revolt in March.