The main Syrian opposition bloc - the High Negotiations Committee (HNC) - has agreed to a 2 to 3 week truce if Russia stops its campaign of air strikes in Syria, a source with knowledge of peace talks being held in Geneva said on Saturday.
The source said the truce, if implemented, would be renewable and supported by all parties except DAESH.
Russian air strikes began on September 30 2015 in support of the regime of Syrian autocrat Bashar al-Assad after months of military gains by rebels in the country. The Russian intervention has since turned the tide of fighting in favour of regime.
Syrian regime forces and the YPG militant group - backed by Russian air strikes - have been making advances against opposition forces in northern Syria in the countryside surrounding the city of Aleppo.
The YPG took control of al Shadadi district in the north eastern province of Hasakah on Friday.
The YPG is the armed wing of the PYD, which Turkey considers to be the Syrian affiliate of the PKK, which is listed as terrorist organisation by Turkey, the US and the EU.
The Syrian conflict, which began with peaceful anti-government protests in March 2011, has drawn in several other countries.
Syria's conflict is now approaching its sixth year, with more than 470,000 people killed so far according to the Syrian Network for Human Rights. More than half of Syria’s population are displaced either internally or outside of the country.