Syria crisis: West seeks 'next steps'
The US has said it is consulting international partners over steps to take over Syria, after UN observers suspended their activities.
Norwegian Gen Robert Mood, the head of the UN Stabilisation Mission (UNSMIS), said observers would cease operations because of the escalating violence.
But he said the mission remained committed to ending the violence.
The UK foreign secretary said the decision called into question the mission's viability.
William Hague blamed the government of President Bashar al-Assad for the worsening situation.
In a statement, he said the suspension of patrols and restriction of staff movements "underlines the extent of the deterioration of security and stability in Syria, and calls into serious question the viability of the UN Mission".
Activists reported on Saturday that at least 60 people had been killed around the country, with the worst violence in areas around Damascus, where they said 10 people were murdered in the town of Saqba.
The announcement came just a day after Gen Mood had rung alarm bells.
He had warned that the escalation of violence in the past 10 days had limited the ability of the observers to do their job of monitoring, verifying and reporting what was going on, and trying to foster dialogue.
It marks a recognition that the Kofi Annan peace plan, of which the observer mission is part, has hit the rocks.
Apart from the general upsurge in violence, the observers have in recent days found themselves physically obstructed, and their vehicles attacked and shot at.
So the suspension is a clear message to the international community that the situation is untenable, and that concerted action is needed to salvage the Annan peace plan, which remains the only template for a peaceful solution.
That means pressure being applied to both sides in their conflict, by their outside allies, to halt the violence and enter dialogue - something at the moment that's hard to imagine.
At least seven people were killed in Douma, an eastern suburb of the capital Damascus, while at least 18 others died in violence elsewhere, the UK-based Syrian Observatory for Human Rights reported.
The opposition Syrian National Council also warned of a looming massacre in Homs which it says is besieged by 30,000 troops and pro-regime militiamen.
Syria restricts access to foreign media, and reports of killings are difficult to verify.
US White House spokesman Tommy Vietor urged Syria to abide by international mediator Kofi Annan's six-point peace plan.
"At this critical juncture, we are consulting with our international partners regarding next steps toward a Syrian-led political transition as called for in Security Council resolutions," he said.
Arab League spokesman Ahmad Bin Hilli told the BBC the decision was a temporary one, and the operation could be cancelled only by the UN in consultation with the Arab League.
Announcing the suspension of UNSMIS operations, Gen Mood said the suspension would be "reviewed on a daily basis" and that a "return to normal operations remains our objective".
The UN Security Council's five permanent members will consider the next steps for the observer mission when Gen Mood briefs them on the situation in Syria on Tuesday.
The mission's 298 military observers and 112 civilian staff were sent to Syria to verify the implementation of the Annan plan, which included a ceasefire.