The truce would open the door for the Syrian opposition's participation in the scheduled Geneva peace talks, which the rebels have said they would boycott because of the government's ongoing offensive.
Turkish Foreign Minister Ahmet Davutoglu met Friday in Ankara with Ahmad al-Jarba, leader of the Syrian National Coalition, which has been locked in a bloody struggle with the Iranian-backed government of President Bashar Assad.
A Turkish diplomat told the Hurriyet Daily News Turkey would formally propose the cease-fire at a meeting of the Friends of Syria this month. Davutoglu and Iranian Foreign Minister Javad Zariff had said in November a cease-fire was necessary to make the Geneva talks work.
A potentially significant clash was reported Friday in northern Syria, where opposition fighters attacked a rival rebel unit affiliated with al-Qaida.
The BBC said Saturday the Islamic State of Iraq in Syria (ISIS) was on the defensive in al-Atareb and Andana, areas that had been strongholds of the Sunni group.
"We have surrounded them in Andana," said a leader of Ahrar al-Sham, an Islamic group within the opposition. "We have told their foreigners that they must come and join us, within 24 hours, or face being killed."
Military analysts told the BBC the opposition turned on ISIS as their successes on the battlefield stalled and ISIS imposed harsh and unpopular Muslim fundamentalism on the areas they controlled.