Syrian opposition fighters and activists cautiously welcomed a deal between the US and Russia that will see a truce between themselves and pro-Assad forces begin on 12 September – the first day of the Islamic holiday, Eid.

Syria's High Negotiations Committee said they hoped it would be enforced to help ease the suffering of civilians.

Russia should pressure Syrian President Bashar Assad to make sure his forces abide with the agreement said Basma Kodmani, a spokesman for the organisation which is made up of a number of opposition groups.

However, opposition fighters were more pessimistic about whether the ceasefire would hold. Fares al-

Fares al-Bayoush, the head of a moderate Free Syrian Army group told the Associated Press (AP) that Assad's forces and their Russian backers had not observed the last ceasefire agreement and were unlikely to abide by this one.

Separately, Captain Abdul Salam Abdul Razak, military spokesman for the rebel Nour al-Din al Zinki Brigades, told the AP that Syrian army would use the break in hostilities to regroup and gather forces for the battle in Syria's second city, Aleppo.

On the ground, the London-based activist group, the Syrian Observatory for Human Rights reported that clashes were continuing between Islamic State (Isis) fighters and government forces in the province around the country's capital Damascus on 10 September. Regime forces had also bombed Aleppo in air strikes, the Observatory reported.

The Syrian government has nonetheless said it is prepared to comply with the deal. Opposition forces have also indicated they will adhere to the requirements of the peace plan, if the Syrian government commits fully to the deal.

US-Russia air strikes

If the truce holds, the US and Russia have said they will begin joint air strikes against agreed terrorist targets.

But following the deal's announcement, the Pentagon warned in a statement that any "potential military cooperation" between the two countries was contingent on the terms of the truce being "fully met".

If it does hold, Russia's foreign minister Sergei Lavrov – who struck the deal with US Secretary of State John Kerry – said the countries will "jointly agree on strikes against terrorists to be carried out by the Russian and American air forces. We have agreed on the zones in which these strikes will be carried out".

"Only the Russian and American air forces will work in these zones," he added.

The deal was welcomed by politicians around the world.

During a phone call with his Turkish counterpart Mevlüt Çavuşoğlu, Lavrov said the pair had agreed it was important for all parties concerned to fulfil the cessation of hostilities in Syria and resume negotiations, in a statement released by Russia's Foreign Ministry.

However, British Foreign Secretary Boris Johnson called on Russia to use all its influence to ensure that the Syrian government complies with its obligations under a diplomatic deal agreed by Moscow and Washington.

"It's vital that the regime in Damascus now delivers on its obligations, and I call on Russia to use all its influence to ensure this happens," he said. "They will be judged by their actions alone."

The European Union's top foreign affairs diplomat, Federica Mogherini, also welcomed the deal and called on the United Nations to prepare proposals for political transition talks in Syria.

"All parties to the conflict, other than groups designated as terrorist organisations by the United Nations Security Council, must now ensure its effective implementation," she said.