World powers and regional states are due to meet on August 17, one day after the United Nations ended its monitoring mission in Syria.
The five permanent Security Council members, plus key Arab states and Turkey, will discuss what steps to take next.
On August 16, deputy UN peacekeeping chief Edmond Mulet said Syria's government and rebels have "chosen the path of war."
The UN decision comes two weeks after former UN Secretary-General Kofi Annan quit as mediator after the failure of a 4-month-old truce.
UN sources said Algerian diplomat Lakhdar Brahimi, a veteran of the troubles in Iraq, Afghanistan, and elsewhere, has agreed to take over as a peacebroker but with an altered mandate.
UN officials said the last of the few dozen remaining team members would quit Damascus by August 24.
Based on reporting by Reuters and AP