The US and Russia have agreed terms for a "cessation of hostilities" in Syria from February 27, in a move to stem the spiralling violence in a civil war into which several foreign powers have been drawn.
The ceasefire plan does not include Isis or al-Qaeda's Syria branch, Jabhat al-Nusra, and leaves open the option for other groups to be excluded if they are deemed "terrorist" organisations by the UN Security Council.
Moscow and Washington, who back rival sides in the conflict, called on other parties to declare their acceptance of the plan by midday, Damascus time, on Friday, February 26.
According to the peace deal, Moscow, which backs Bashar al-Assad, the Syrian president, and Washington, which backs the rebels fighting to oust him, would set up a communication hotline and, potentially, a "working group" to ensure the plan's implementation and the honouring by their sides of the ceasefire.
John Kerry, US secretary of state, called on all sides to accept the deal. "If implemented and adhered to, this cessation will not only lead to a decline in violence but also continue to expand the delivery of urgently needed humanitarian supplies to besieged areas and support a political transition to a government that is responsive to the desires of the Syrian people," he said.
Vladimir Putin, Russian president, said it was essential that Russia and the US, as co-chairs of the International Support Group for Syria, were ready to effectively monitor implementation of the ceasefire by both the Syrian government and armed opposition groups.
The agreement "could become an example for responsible joint action of the international community," he said, in a statement.
Late on Monday, the High Negotiations Council, which represents the opposition in peace talks, issued a statement indicating it had accepted the terms of the cessation of hostilities.
Meanwhile, Mr Assad, called a parliamentary election for April 13, according to a statement issued by the presidency on Monday. Syria's last parliamentary election was in 2012 and they are held every four years.
A ceasefire is critical for Syria, whose war has killed about 300,000 people and displaced half the population. Russia and Iran have intervened military on behalf of Mr Assad while a US-led coalition has bombed Isis in the east. Most recently, Turkey has targeted Syrian Kurdish militants advancing near its border.
However, plenty of scepticism surrounds the plan. This month, peace talks sponsored by Washington and Moscow collapsed as Assad forces launched an offensive under Russian air cover to capture rebel strongholds in the north, forcing tens of thousands of civilians to flee.
Moreover, the deal does not rule out air strikes, a clause that rebels fear will be used against them. It does not prevent outside powers providing military aid to the warring parties. Mr Assad said on Sunday he would accept a ceasefire as long as "terrorists" did not use it to improve their positions, specifically pointing to a halt in weapons supplies. Damascus defines all rebel groups fighting it as terrorists.
It is unclear how Syria's US-backed Kurdish militants, who have been carving out an autonomous region in the north, will react to the ceasefire plan. The deal calls for all parties to stop seizing territory but the Kurds have been taking land from rebel forces in Aleppo's countryside on the grounds that the fighters were tied to Jabhat al-Nusra. ]
Mr Kerry made no mention of Mr Assad's fate or Russia's increased air strikes in recent weeks. This is likely to anger opposition groups that are already at odds with the US after it pushed them to go to the failed negotiations in Geneva.
"If there was trust this would be different but right now there is no trust — not in Russia and not even in the international community," said Yasser al-Youssef, a political representative of the Nour al-Din al-Zinki brigades in Aleppo.
"Before this deal, Russia said they were intervening to stop Isis and 90 per cent of the time it was us rebels or civilians who got hit," Mr Youssef said.
The rebels have yet to decide on their position regarding the ceasefire, as does Mr Assad.