The highest ranking Syrian diplomat to date has defected to the opposition. Nawaf Fares, Syrian ambassador to Iraq, announced at a press conference that he was joining the rebellion against President Assad.
The move comes just a week after a Syrian general from a powerful family close to President Assad also defected.
Meanwhile Western nations are urging the UN to threaten tough sanctions against Syria as the Security Council opens talks on the future of its observer mission in the country.
The Security Council must pass a new resolution before the mission's mandate ends on Friday next week.
Mr Fares confirmed his defection in a statement broadcast on al-Jazeera TV.
With Syrian revolutionary flags behind him, he read out the statement saying: "I announce my resignation from my post as ambassador of the Syrian Arab Republic to the brotherly republic of Iraq."
He also announced he was quitting Syria's ruling Baath party.
Mr Fares described the situation in Syria as a "horrific massacre by the criminals of a brutal regime".
He said he believed that there was no longer any hope of real reform.
Mr Fares - a former governor of several provinces - was appointed ambassador to Baghdad in 2008. He was the first Syrian envoy to Iraq for nearly three decades, because of bad relations between the two countries.
The BBC's Jim Muir in neighbouring Lebanon says, significantly, he is also chief of a Sunni tribe, the Uqaydat, which straddles Syria's eastern border with Iraq.
Fares was apparently not a member of the inner circle, but his defection may give other diplomats the idea. A few high ranking defections may start the ball rolling elsewhere as the rats begin to abandon a sinking ship.