A new deal between the US and Russia to enforce a ceasefire in Syria has been reached, with the cessation of hostilities set to come into force on 27 February.

The ceasefire, subject to the agreement between the warring parties, would exclude Islamic State, al-Nusra Front and other groups deemed to be terrorist organizations.

Skepticism about whether it can be enforced will be widespread after a previous planned ceasefire failed to take place. Instead, Russia continued its bombing campaign, sieges of starving towns were never lifted and other confidence-building measures ignored.

But the joint statement by Russia and America will not have been issued on Monday – following extensive talks – unless the two countries had relatively clear indications that its terms will be accepted by the key plays including the Syrian government, the opposition forces sponsored by Saudi Arabia, and by Syrian Kurds.

In a change to the previous aborted ceasefire, Russia and America have agreed to act as direct guarantors and monitors of the cessation of hostilities.

In a joint statement Russia and America said the cessation of hostilities would begin at midnight on Friday 27 February Damascus time, requiring parties to the agreement to indicate acceptance by noon the day before.

Key to the agreement issued on Monday will be co-ordination between Washington and Moscow to set out territories that are subject to the ceasefire, and therefore must not be subject to aerial bombing by Russia, attacks by the Syrian army or the American backed opposition. In view of the intricate interweaving of the various factions, the shifting alliances and complexity of the front lines in Syria, communication between Russia and the US on the precise territory subject to a ceasefire will have to be tightly coordinated. The likelihood that either artillery fire or aerial bombardment will deliberately or inadvertently land in territory party to the ceasefire is high.

The agreement states violations of the ceasefire will be reported on a hotline to a special task force co-chaired by America and Russia which will have power to determine a group can no longer be deemed party to the agreement, and so once again open to military attack.