The U.N.-Arab League’s special envoy to Syria, former United Nations secretary general Kofi Annan, told the international body today that the year-long conflict must end by 06:00 a.m local time on April 12 if President Bashar al-Assad’s regime agrees to the April 10 deadline to pull back its military forces from population centers. Reuters reports:

“The government and the opposition commanders [must] issue clear instructions so that the message reaches across the country, down to the fighter and soldier at the local level.”

“We must silence the tanks, helicopters, mortars, guns and stop all other forms of violence too – sexual abuse, torture, executions, abductions, destruction of homes, forced displacement and other abuses, including on children,” Annan said.

Syrian authorities told Annan today that they have begun the military withdrawal from cities but an opposition figure questioned the government’s claim:

“They are complete liars, there is no army withdrawal, they are still in the middle of the city. They fired on the city this morning, like they do every day,” a man calling himself Abu Mustafa said by telephone from Zabadani near the Lebanon border.

However, he did acknowledge a modest pullback. “The army withdrew 15 tanks yesterday, but the rest are all around the checkpoints as usual,” Abu Mustafa said.

The Syrian government agreed to the April 10 deadline to implement Annan’s so-called “six point plan” which calls for a U.N.-supervised ceasefire by government and opposition forces, withdrawal of soldiers and heavy weapons from cities, and delivery of humanitarian aid.

The U.S. ambassador to the U.N. Susan Rice said yesterday that she is “skeptical” that Assad will adhere to any commitments to end the violence. “From the US point of view, and I think the point of view of many member states, what we have seen since 1 April is not encouraging,” she said.