The United Nations Secretary General Ban Ki-moon has said the situation in Syria remains "highly precarious".
The UN has reached a preliminary deal with the Syrian government on rules governing the deployment of observers to monitor an agreed ceasefire.
Ban said he has seen "troubling" evidence of ongoing violence and wants the UN observer mission to increase to 300, to be deployed over three months.
Some correspondents say the Security Council, which is not due to make a decision on the mission until next week, may be afraid to put unarmed observers on the ground if the situation continues to deteriorate.
The UN chief said such a deployment would not be without risk, but UN supervision, with a clear mandate and the right capacity, would contribute to improving the situation on the ground.
Meanwhile, US Secretary of State Hillary Clinton called for a global arms embargo and further sanctions if the government continues to break the ceasefire.
Foreign ministers from the Friends of Syria coalition, meeting in Paris last evening, agreed that the ceasefire and Kofi Annan's six-point peace plan were the "last hope" of avoiding civil war in Syria.