Russia said on Tuesday that President Bashar al-Assad was "fully committed" to ending the bloodshed in Syria, as his regime pounded the city of Homs for a fourth day and vowed no let-up.
As several European nations pulled their ambassadors from Syria, a top US senator called for the arming of rebels fighting Assad's rule and Washington said it was exploring options for providing humanitarian aid.
Tank and artillery fire rained on Homs, killing at least 15 civilians, activists said, as the interior ministry vowed to keep up its onslaught against "terrorist groups".
"There are about four blasts every five minutes," said Abu Rami, an activist in Homs reached by AFP by telephone from Beirut. "The humanitarian situation is dire. No one can move around."
An interior ministry statement carried by the SANA news agency pledged that "operations to hunt down terrorist groups will continue until security and order are re-established in all neighbourhoods of Homs and its environs."
More than 6,000 people have died in nearly a year of upheaval in the Middle East country, as Assad's hardline regime seeks to snuff out a revolt that began with peaceful protests in March 2011 amid the Arab Spring.
Russian Foreign Minister Sergei Lavrov flew into Damascus to a hero's welcome on Tuesday, with thousands of cheering, flag-waving Assad supporters lining the route of his motorcade.
Russia, which along with China over the weekend vetoed a UN resolution condemning the government crackdown, has staunchly stood by its last ally in the region, a key buyer of Moscow's military hardware that hosts a strategic Russian naval base.
"We (Russia) confirmed our readiness to act for a rapid solution to the crisis based on the plan put forward by the Arab League," said Lavrov, adding Syria was ready to see an enlarged Arab League mission in the country, Russian news agencies reported.
"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.
"In particular, President Assad assured (us) that he is fully committed to the task of a cessation of violence, from whatever source it comes."
The 22-member Arab League deployed an observer mission to Syria in December to oversee a plan to end the bloodshed, but it was suspended a month later amid increasing violence on the ground.
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It 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 Tuesday's talks with Lavrov, the official SANA news agency said.
Lavrov did not specify which of the two Arab plans he was referring to in his comments Tuesday, although SANA quoted Assad as interpreting the reference to be to the earlier one.
Lavrov said Syria was pressing ahead with the reform programme 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... 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.
In Washington US 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.
White House spokesman Jay Carney said that the US was consulting with allies to discuss how to provide humanitarian aid.
"We are exploring the possibility of providing humanitarian aid to Syrians," he said, admitting that no "mechanisms" currently existed for delivering such aid.
Said State Department's Nuland: "Some of these proposals that people are brooding about could not be done without foreign military intervention -- as we have said, we don't think more arms into Syria is the right answer."
A day after the United States closed its Damascus embassy, France, Italy, the Netherlands and Spain joined Britain and Belgium on Tuesday in recalling their ambassadors to Syria for consultations.
Turkey, a former Assad ally which shared Western anger over the Russian and Chinese vetoes, said it would launch a "new initiative" with like-minded countries which "stand by the Syrian people, not the regime."
And the six Arab states of the Gulf announced that they had decided to expel Syria's envoys and withdraw their own from Damascus in protest over the "mass slaughter" of civilians.