UN-Arab League envoy Kofi Annan appealed to the Security Council to use its leverage to prevent the collapse of his efforts to end Syria's conflict after Damascus ignored a deadline to withdraw troops from towns.

Several Western diplomats complained privately that Damascus appeared to have won a two-day extension after flouting its first deadline under Annan's peace plan. But they said it was vital to keep the 15-nation body, which has faced deep rifts over Syria, united in order to maintain pressure on Damascus. 

"Every effort must be made to achieve a cessation of violence in all its forms on 12 April at 0600 (0300 GMT)," Annan told the council in a letter, obtained by Reuters.

"There is no more time to lose," Annan said in a statement to the press. "We must all push for an end to the bloodshed before Syria plunges into the abyss."     

US Ambassador to the United Nations Susan Rice, president of the council this month, said all council members voiced "deep concern" at Damascus' level of commitment to its truce pledges.
She was speaking to reporters after Annan's deputy Jean-Marie Guehenno briefed the council via video link from Geneva.

Rice added that the council may soon face a "moment of truth" when it will have to decide whether to increase pressure on the government of Syrian President Bashar al-Assad, who has shown no signs of complying with a Tuesday deadline to withdraw forces from towns and stop using heavy weapons.

Her remarks appeared to be aimed primarily at Russia and China, which have twice vetoed Western- and Arab-backed resolutions condemning Assad's 13-month assault on pro-democracy protesters but have recently supported several council statements backing Annan's six-point peace plan.

"The US view is that it is outrageous but by no means unexpected or surprising that the (Syrian) government has yet again made commitments and broken them," Rice said.   

The former UN secretary-general was far from optimistic in his assessment of the situation in Syria, where the United Nations says more than 9,000 people have been killed by Syrian security forces since March 2011. Damascus says rebels have killed more than 2,500 soldiers and security personnel.

"I am gravely concerned at the course of events," Annan said in his letter. "The days before 10 April should have been an opportunity for the Government of Syria to send a powerful political signal of peace, with action on all aspects of the six-point (peace) plan," he wrote.

Damascus had agreed to a Security Council-backed Tuesday deadline to withdraw troops from and stop using heavy weapons against Syrian towns, to be followed by a full ceasefire by the army and rebels on Thursday morning.

However, Syrian troops killed 31 people on Tuesday, pursuing a fierce assault on Assad's opponents instead of silencing their big guns and leaving towns as promised under Annan's peace plan.

Annan said Damascus should have taken steps "to cease troop movements towards population centers, to cease all use of heavy weapons in such centers, and to begin pullback of military concentrations in and around population centers." This had not happened, Annan said.

"In the last five days it has become clear that such a signal has yet to be issued," he wrote to the council. "While some troops and heavy weapons have been withdrawn from some localities, this appears to be often limited to a repositioning of heavy weapons that keeps cities within firing range," he said.

"Furthermore, several new localities also appear to have been subject to military operations, including the use of heavy weapons on population centers," he said.

Annan made clear that there was still a chance to salvage his efforts to secure an end to the violence by Thursday's 0300 GMT deadline for the government and opposition to stop fighting. "The Syrian leadership should now seize the opportunity to make a fundamental change of course," he said.

"It is essential that the next 48 hours bring visible signs of immediate and indisputable change in the military posture of the government forces throughout the country," Annan said.

He added that the opposition should also cease fighting in order to "give no excuse for the government to renege on its commitments." - Reuters