UNITED NATIONS - Syria has agreed to an April 10 deadline to begin implementing a six-point peace plan, UN-Arab League envoy Kofi Annan told the UN Security Council on Monday, according to the 15-member body’s president for April, US Ambassador Susan Rice.

The plan calls for a UN-supervised ceasefire by all parties, withdrawal of soldiers and heavy weapons from cities, and delivery of humanitarian aid. Annan, who was briefing the UN Security Council in closed session, has asked the Security Council for its backing of next Tuesday’s deadline for Syria to partially implement his peace plan, with a full ceasefire within 48 hours.

Rice said Annan told the Council that he received this timetable from Syria’s foreign minister on Sunday and indicated that he would have preferred an earlier deadline. She said Annan urged the Syrian government to start the withdrawal earlier and move no further into populated areas. Syria’s UN Ambassador Bashar Jaafari said the April 10 deadline was set “by common accord” between Annan and the Syrian govt. But he added his govt expects the same commitment from the opposition.

“The Syrian government is committed, but we are expecting Mr. Kofi Annan and some parties in the Security Council also to get the same kind of commitments from the other side (opposition). A plan wouldn’t be successful unless everybody is committed to it,” said Jaafari.

Rice said: “We have seen promises made and promises broken.” Past experience “would lead us to be sceptical” that Syria would implement the Annan plan, Ms Rice said, warning that it was possible violence might escalate instead.

AFP adds: Russia has rejected the idea of a deadline, with Foreign Minister Sergei Lavrov saying “ultimatums and artificial deadlines rarely help matters.”

Moscow, a Soviet-era ally of the Assad regime, said only the UN Security Council, where it wields veto power, could put any time restrictions on Syria’s compliance with the Annan plan.

“The demands should be put to all sides of the barricades,” Lavrov said. “We intend to be friends with both sides in Syria,” he said of Russia’s support for Assad. International Committee of the Red Cross (ICRC) president Jakob Kellenberger, meanwhile, was making his third visit to Syria since 2011, as monitors and activists said at least 18 more people, mostly civilians, were killed on Monday. Kellenberger said he would meet officials including Foreign Minister Walid Muallem and examine measures for a two-hour humanitarian ceasefire, also a condition set out in the Annan plan.

Colonel Kassem Saadeddine, spokesman of the rebel Free Syrian Army, accused the world of failing to protect Syrians, saying it was ignoring the Assad regime’s “massacres” by refusing to arm the insurgents.

On Monday, security forces pressed their crackdown on dissent, with 10 civilians, five rebel fighters and three soldiers among those killed across Syria, monitors and activists said.

Meanwhile, NATO’s chief on Monday said the alliance was opposed to providing arms to the Syrian opposition seeking to counter a regime crackdown, warning that it would fuel a proliferation of weapons in the region.

Anders Fogh Rasmussen called for a diplomatic solution and reiterated that NATO  had “no intention whatsoever to intervene in Syria.”