A UN team sent by peace broker Kofi Annan arrived in Syria on Thursday to pave the way for observers, as the Security Council backed an April 10 deadline for the regime to end its deadly crackdown.
The developments came as Annan said the Syrian government had announced a partial withdrawal from protest cities, but that this had not been confirmed and that "alarming levels" of deaths were still being reported.
The Syrian Observatory for Human Rights said there was no sign of withdrawals, with regime forces launching fresh assaults on rebel strongholds, and that 58 people were killed nationwide, among them 35 civilians including three children.
Most of the civilians were killed in the central Homs province, it said, but fatalities were also reported in Douma near Damascus, in the northern provinces of Idlib and Aleppo and in the southern province of Daraa.
The Britain-based monitoring group said that 22 soldiers and one deserter also died in clashes, many in Homs.
The advance UN team headed by Norwegian General Robert Mood, a Middle East specialist, will discuss with the authorities "the modalities of the eventual deployment of the UN supervising mission," Annan spokesman Ahmad Fawzi said.
Annan told the Security Council on Monday it should consider whether to send a mission to monitor events in Syria, where activists say more than 10,000 people have been killed since March 2011 in the crackdown on dissent.
Fawzi said the observers can be sent only after a Security Council resolution ordering their deployment.
The council formally backed the April 10 deadline that former UN chief Annan agreed with Damascus to end its military offensive on protest cities.
A statement called on Damascus to "begin pullback of military concentrations in and around population centres, and to fulfil these in their entirety by no later than April 10, 2012."
It also called "upon all parties, including the opposition, to cease armed violence in all its forms" within 48 hours of the above being implemented.
In remarks to the UN General Assembly, Annan urged the "government and the opposition commanders to issue clear instructions so that the message reaches across the country down to the fighter and soldier at the local level.
"It is clear that more far-reaching action is urgently required. Immediate and verifiable steps are needed to complete implementation of commitments in the crucial days ahead," he said.
"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."
Signup to our newsletter and follow us on Facebook and Twitter!
Annan said opposition groups his team had spoken to had "committed to call for cessation of violence once the Syrian government has demonstrably fulfilled its commitments."
US State Department spokesman Mark Toner said Washington saw no signs that Assad's forces were complying with the peace plan.
"It is clear that the Assad regime appears to be using this window to continue to carry out its horrible assault on the Syrian people," he said.
"The punishment for non-compliance is going to be increased pressure on Assad, on his regime, and a clear message to those around him that they are on the wrong side of history," Toner said.
Earlier, pro-government daily Al-Watan quoted an unnamed government official as saying Damascus is not bound by a deadline.
"April 10 is the date set for the beginning, not the end, of the withdrawal of troops and it does not constitute a deadline," it said.
French Foreign Minister Alain Juppe said he had little confidence Annan's plan would end the repression.
"Can we be optimistic? I'm not," Juppe told reporters in Paris.
"I think Bashar Al-Assad is cheating us. He is pretending to accept Kofi Annan's six-point peace plan but at the same time he continues to use force."
Russian Foreign Minister Sergei Lavrov warned the West against issuing ultimatums to Damascus.
"The Syrian government has accepted (Annan's) proposals, has begun implementing them, and it is very important right now not to undermine this process through ultimatums and threats and unfortunately there are those who'd like to do that," he said.
The foreign ministry said Lavrov told Annan by telephone that Moscow backed Thursday's Security Council statement with the understanding that a second deadline for the opposition to lay down weapons would also be imposed.
The surge in violence has sent Syrians fleeing, with an official in Ankara saying more than 1,000 people had crossed the border in the past 24 hours, bringing to nearly 21,000 the number of Syrian refugees now in Turkey.
Meanwhile, Syria has agreed to provide access to detention facilities throughout the country, International Committee of the Red Cross chief Jakob Kellenberger said on Thursday after a two-day visit to Damascus.