Many rebel leaders he contacted had also agreed to a truce during the holiday, which starts on Friday, he told reporters in Cairo after meeting Arab League chief Nabil al-Arabi.

The Syrian government would officially announce its acceptance by Thursday, he added.

He added that "most" rebel leaders contacted said they would observe a truce, but did not specify if this included commanders of the main rebel group, the Free Syrian Army.

"If we succeed with this modest initiative, a longer ceasefire can be built on it, and the launch of a political process," Brahimi said.