Turkey PM Recep Tayyip Erdogan has accused the United Nations Security Council (UNSC) of indirectly supporting the oppression of the Syrian people by failing to unite on Syria.
Mr Erdogan said the UNSC was standing by with its "hands and arms tied" while the Syrian people were dying every day.
Russia says Syria has promised to pull its forces from cities by 10 April.
America's UN ambassador says the UNSC is drafting a statement to support special envoy Kofi Annan's peace plan.
The statement will be discussed by the 15-nation council over the next two days, Susan Rice said, according to Reuters news agency.
Mr Annan, the UN and Arab League envoy, told council members on Monday that the Syrian government had agreed to halt its military operations over a period beginning on Sunday and ending by 10 April.
But Ms Rice said the actions of the regime since 1 April had not been encouraging.
She said if the authorities used this window of opportunity to intensify rather than decrease violence, the Security Council would need to respond in an "urgent and serious way".
She acknowledged the council was divided over taking action to pressure Damascus.
But she suggested that if the Syrian government continued its military offensive despite its commitment to Mr Annan's peace plan, the diplomatic calculations of Syria's allies might change, reports the BBC's Barbara Plett at the UN.
Meanwhile, the president of the UN General Assembly, Nassir Abdulaziz al-Nasser, says he has asked Mr Annan to brief the world body on his Syria peace mission.
No date has been set, but Mr Nasser said he had suggested 13 April, our correspondent reports.
In Damascus, the head of Red Cross, Jakob Kellenberger, has been meeting top Syrian officials to try to get Syria to allow aid workers better access to those who have been wounded or displaced by the conflict.
Mr Kellenberger is also pressing the Syrian authorities to implement a daily two-hour ceasefire, as stipulated in the peace plan proposed by Mr Annan.
Russia's foreign ministry says Syria's government has informed Moscow it has started implementing Mr Annan's plan to end the unrest.
The ministry said in a statement that the Syrian ambassador to Moscow told Russia's Deputy Foreign Minister Mikhail Bogdanov that Damascus had begun fulfilling its obligations under the plan, the Associated Press news agency reports.
The statement did not give any further details.
Mr Erdogan said by not taking a decision on Syria, the UN Security Council had "indirectly supported the oppression. To stand by with your hands and arms tied while the Syrian people are dying every day is to support the oppression".
He told members of parliament from his governing AK Party that Turkey would not turn its back on the Syrian people.
China and Russia have twice vetoed resolutions condemning President Bashar al-Assad's regime for turning the army on civilians.
On Monday, Mr Annan told the UN Security Council that President Assad had agreed to withdraw security forces from major population centres by 10 April.
He also asked the council to plan for the deployment of UN observers to supervise the ceasefire by all parties, as set out in his peace plan.
UN officials and diplomats said the monitors would probably be drawn from other peacekeeping forces in the region and could not be established without an end to the fighting, agreement by all parties and a Security Council mandate.
An advance team from the UN's Department of Peacekeeping Operations (DPKO) is expected to arrive in Damascus imminently to discuss the deployment of international monitors.
The ceasefire is only one part of Mr Annan's peace plan, which also calls for a political process to address the "aspirations" of the Syrian people, release of detainees, delivery of humanitarian aid, free movement for journalists, and right to protest.
Activists say government forces have continued to attack opposition strongholds despite Damascus's pledge to observe the peace plan.