AhlulBayt News Agency - A number of Syrian opposition groups have declared that they agree to the "possibility" of a temporary truce if President Bashar al-Assad's government and its allies respect several conditions, including halting fire.
The groups said on Saturday they would agree provided there were guarantees that the Syrian government forces and its allies would respect a ceasefire, sieges were lifted and aid deliveries permitted across the country.
The announcement came as fighting continued on the ground despite a Friday deadline for cessation of hostilities.
Russian fighter jets are repeatedly striking rebel targets, particularly in Aleppo, backing government forces as they push towards Syria's second city.
The opposition factions "expressed agreement on the possibility of reaching a temporary truce deal, to be reached through international mediation", a statement from the High Negotiations Committee said.
It said the UN must guarantee "holding Russia and Iran and sectarian militias ... to a halt to fighting".
All sides should cease fire simultaneously and the government should release prisoners, the statement said.
The UN is struggling to deliver aid to about 4.5 million Syrians who live in hard-to-reach areas, including nearly 400,000 people in besieged areas.
It also expressed "regret" that a planned UN Security Council resolution cautioning against a Turkish ground invasion was rejected on Friday, and said it was "concerned at the growing tension at the Syrian-Turkish border".
It said UN-led talks planned for Saturday between major international players on a ceasefire in Syria had been postponed.
Maria Zakharova, Russian foreign ministry spokeswoman, told Russian news agencies the meeting in Geneva had been put back to an unspecified later date as "consultations" between key nations continued.
Military and diplomatic officials from Russia and the US held talks on Friday to try to finalise the details of a possible ceasefire, as a hoped-for halt in hostilities on the ground failed to materialise.
That gathering was supposed to pave the way for a broader meeting after the 17 key international players involved in negotiations to end the Syrian conflict agreed on January 12 that a ceasefire should come into force within a week.
The truce failed to take effect on Friday as fighting continued in Syria, with Kurdish-led forces backed by US-led air power seizing a key town from the ISIL.
