Beirut: A key Syria opposition umbrella group on Saturday said it would agree a temporary truce proposed by world powers on several conditions, including that regime allies Russia and Iran halt fire.
In a statement, the High Negotiations Committee (HNC) also made its acceptance of the so-called "cessation of hostilities" conditional on the lifting of sieges and the delivery of humanitarian aid.
"The rebel factions agreed in principle on the possibility of reaching a temporary ceasefire provided it is done with international mediation and with guarantees obliging Russia, Iran and their sectarian militias and mercenaries to stop fighting," HNC chief Riad Hijab said in a statement.
The HNC is an umbrella group of political opposition bodies and rebel factions that was formed to participate in negotiations with the regime that collapsed earlier this month.
After the talks fell apart, world powers last week proposed a ceasefire as part of a plan that also included expanded humanitarian access.
The truce was meant to have gone into effect by Friday, but little progress has so far been made towards even a temporary halt to the fighting, which has only intensified in recent days.
The statement, issued after a meeting of the HNC, said the opposition "wants to respond positively to international efforts to stop the Syrian bloodbath".
"But... there will not be a truce unless fighting stops simultaneously on the part of all the belligerents, sieges are lifted, humanitarian aid is delivered to those in need, and prisoners, particularly women and children, are released," it said.
Regime backer Russia and opposition supporter Washington are meant to be co-chairing a UN panel that is working on the modalities of the temporary truce.
Officials from the two sides met for talks on the issue on Friday, but no official plan has been laid out, nor has a start date been proposed for a truce.
In recent days, fighting has intensified in Syria, particularly in northern Aleppo province, where rebel forces have lost ground to both regime forces backed by Russian air power and a Kurdish-led coalition called the Syrian Democratic Forces.
Syria`s conflict is now approaching its sixth year, after beginning with anti-government protests in March 2011.
It now involves an array of groups including moderate and Islamist rebels, jihadists from Al-Qaeda affiliate Al-Nusra Front and the Islamic State group, the Kurds, and regime forces backed by Russia and Iran and Lebanon`s Hezbollah movement.
More than 260,000 people have been killed in the conflict, and half the country`s population has been displaced.