Reports of the defection of a general and personal friend of Bashar al-Assad will cheer the Syrian leader's enemies at an upcoming meeting in Paris of the Western and Arab states that want to drive him from power.
A source in the exiled opposition said Manaf Tlas, a brigade commander in Assad's Republican Guard, was en route to Paris where the "Friends of Syria" group of states opposed to Assad was due to meet. He has family there.
If he throws his support behind the opposition, Tlas - who attended military college with the 46-year-old Assad - would be the closest member of the Syrian leader's inner circle to switch sides during a 16-month uprising that is now becoming a civil war with strong sectarian overtones.
Tlas, whose father served for decades as defence minister under Assad's father, is a Sunni Muslim, from the majority community which has been the focus of the uprising against a ruling class rooted in Assad's minority Alawite sect.
Opposition activists say Tlas will soon announce that he abandoned Assad because of anger at civilian deaths.
A witness in Damascus said by telephone that Tlas's house in Damascus was ransacked by security agents after reports he had fled the country.
Western governments, which are keen to bring down Assad but have shown no appetite for assuming a direct role like the NATO bombing that helped oust Libya's Muammar Gaddafi last year, will relish the sign of a split among Assad's confidants.
"His defection is big news because it shows that the inner circle is disintegrating," said a Western diplomat who knew Tlas in Damascus. "Manaf does not give the impression that he is a big thug, but he mattered in the military."
In Washington, a US official speaking on condition of anonymity, said, "General Tlas is a big name and his apparent decision to ditch Assad hurts, even though it probably didn't come as a surprise.
"Tlas lately seems to have been on the outs, but he's got charisma and some smarts. If he joins the insurgents that could be significant."
Foreign Minister Ahmet Davutoglu of Turkey, Syria's NATO-member neighbour which has become Assad's most outspoken foe, said defections proved that the Syrian government is crumbling.
"There are soldiers escaping, they are reporting to us that they are being instructed to attack people and because of that they had to escape in order not to kill civilians," he told France 24 television.
"Every day, generals, colonels, officers are coming, and we have, I think, around 20 generals and maybe 100 high-rank officers, colonels."
Turkey has moved artillery and troops towards its border with Syria in the past two weeks since Syria shot down a Turkish warplane at the frontier. Turkey now says it will treat Syrian units that approach the border as hostile.
With heavy fighting now reaching the outskirts of the capital, events on the ground are outstripping the stalled efforts of major-power diplomats.
PEACE PLAN A DEAD LETTER
A peace plan proposed by international envoy Kofi Annan, a former UN secretary-general, has proven a dead letter, with his proposed ceasefire ignored and a small, unarmed UN monitoring team forced to suspend its work.
French President Francois Hollande will open the third meeting of the "Friends of Syria" group, putting the onus on him to take the kind of high-profile role eight weeks into his term that predecessor Nicolas Sarkozy did in the Libyan crisis.
US Secretary of State Hillary Clinton and Britain's William Hague will be among the foreign ministers and delegates from about 50 nations. But Assad's UN veto-wielding allies Russia and China are boycotting a meeting they say is one-sided, and his main regional ally Iran has not been invited.
"Resolving the Syria issue will require the joint effort and participation of all parties in Syria. Right now, China is not considering participating in this meeting," Chinese foreign ministry spokesman Liu Weimin told reporters in Beijing.
As Clinton arrived in Paris, senior US officials said they hoped the talks would endorse recent transition planning by the Syrian opposition and pave the way for discussions at the UN Security Council as early as next week about economic sanctions against the Assad regime.
However, they were unable to say whether Russia and China, which have used their vetoes to block action on Syria in the past, would support putting more pressure on Assad in a new Security Council resolution.
"What form will that pressure take? We - and we believe most of the countries that'll be represented in Paris - think that has to include Chapter VII economic sanctions on Assad," a senior State Department official told reporters.
"That is the argument that we will continue to make to Russia and China," the official, who spoke on condition of anonymity, said.
Neither Russia nor China is expected to attend the Paris meeting, which US officials said they had been told by their French hosts could include around 80 delegations, some 40 of them led by foreign ministers.
When Russian and Chinese delegates attended a broader meeting in Geneva last Saturday, convoked by Annan, they blocked language calling for Assad to step down. They have repeatedly blocked such language in UN Security Council resolutions.
Friday's (Saturday NZT) meeting will focus on ways to support Syrian rebels and provide humanitarian aid. Saudi Arabia and Qatar want to fund and arm Syrian rebels, but Western powers have misgivings about the wisdom of sending more weapons into what could become a wider sectarian conflict.
Syrian troops have pushed into the rebel-held northern town of Khan Sheikhoun, activists said, in an armoured assault that added 11 more victims to a death toll dissidents and Western leaders put at more than 15,000.
With rebels having made some territorial gains in recent weeks, a senior French diplomat said there were signs that even Moscow was now envisaging a post-Assad Syria, something Russian officials strongly deny.
"The situation on the ground has changed fast over the past three weeks, with security forces having no access to some areas. Those areas are not very large but some are connected," the French diplomat said.
"We are now hearing things from within political and military circles in Russia that are surprising us and that we were not hearing before."