BEIRUT — U.S. and world leaders dramatically increased pressure on Syria in the wake of a civilian massacre, with special envoy Kofi Annan declaring the country to be at a tipping point and urging its president to implement a peace plan that could fatally weaken his grip on power.
Annan spoke Tuesday in the Syrian capital as a group of nations — including the United States, Britain, France and Australia — expelled Syrian diplomats in an orchestrated response to last week's massacre of more than 100 people, the majority of them women and children, in the central Syrian township of Houla.
Most of the victims were initially thought to have died in government shelling, but the U.N. human rights office said Tuesday that evidence indicated most were summarily executed in a house-to-house rampage Friday. The U.N. said residents who were interviewed blamed shabiha, pro-government militiamen who rights groups say have acted as regime enforcers and executioners.
The Syrian government has denied responsibility for the massacre, whose graphic images of bloodied and mangled corpses have prompted global revulsion. State Department spokeswoman Victoria Nuland on Tuesday condemned what she called an "absolutely indefensible, vile, despicable massacre."
Nuland said the United States would look for ways to "tighten the noose" around the regime of President Bashar Assad.
Germany and Britain said they were expelling the Syrian ambassadors to their countries, and the U.S. said it was giving the charge d'affaires, the top Syrian diplomat in Washington, 72 hours to leave.
Adding to the pressure, Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, suggested in an interview with Fox News that escalating "atrocities" in Syria could lead to military intervention. The U.S. and its allies, which launched an intensive bombing campaign that helped bring down Libyan leader Moammar Kadafi last year, have generally downplayed the possibility of intervention in Syria.
Annan called on the government and "all government-backed militias" to "stop all military operations and show maximum restraint."
"We are at a tipping point. The Syrian people do not want the future to be one of bloodshed and division. Yet the killings continue and the abuses are still with us today," he said.
The special envoy did not say what consequences the government would face for defying the peace effort.
"For the sake of Syria, and for the region, we must end this violence and begin to restore hope in a political transition to a democratic future," Annan said.
It is still far from certain whether Western countries have the appetite to intervene. But some analysts said Syria's president appeared more boxed in now than at any time during the 14-month rebellion.
"Houla was really a watershed," said Fawaz Gerges, who heads the Middle East Center at the London School of Economics. "Assad is in a very precarious position right now.... If I were President Assad in Damascus, I would think twice before I do the same thing I have been doing for the past 12 months."
Before Friday's massacre, Assad seemed to have reached a stable position, pursuing what he called political reforms but which his critics dismissed as window dressing. Meanwhile, he used his powerful security apparatus to put down the rebellious masses. On the international front, he could count on the protection of Moscow.
But Russia is heavily invested in the U.N. peace plan, which calls for Assad to pull his troops and heavy weapons out of Syria's cities.
The opposition has been skeptical of Annan's peace plan, generally viewing it as a smoke screen for Assad to buy time and placate his international patrons. Complying with the plan now, however, would carry profound risks for Assad. The opposition will benefit if he is pressured to withdraw forces, allow freedom of expression and release political prisoners, all mandates of the U.N.'s six-point peace plan.
True compliance would allow Syrians to demonstrate freely, a scenario that would open the door for opposition forces to exert control over large parts of Syria that are sympathetic to the uprising.
"For Assad, the Annan plan is political suicide," Gerges said. "He cannot afford to pull out his armor. He cannot afford to allow demonstrations on a daily basis. That means he will lose control. It would be like Tunisia or Egypt."
On the other hand, if Assad does nothing he risks alienating Russia, which has vetoed two efforts by the U.N. Security Council to condemn his crackdown on protesters and stands in the way of toughening economic sanctions, trade restrictions and other punishment already imposed on Syria.