A planned ceasefire to end the bloodshed in Syria will come in to effect on 27 February, the US and Russia have announced.
Vladimir Putin hailed the agreement with optimism, describing it as a "real step forward that can stop the bloodshed", and saying Moscow would use its influence on President Bashar al-Assad to try make sure it is observed.
"We will do whatever is necessary with Damascus, with the legitimate Syrian authorities," the Russian President said during a televised address, AFP reports.
In a statement, the White House said Mr Putin and Barack Obama had discussed the deal over the phone. The US said Mr Obama remained committed to "the shared goal of degrading and ultimately destroying Isis", which is not covered by the ceasefire.
It said the truce will apply “to those parties to the Syrian conflict that have indicated their commitment to and acceptance of its terms.”
This does not include Isis, the al-Qaeda-linked Nusra Front and "other terrorist organisations designated by the UN".
Air strikes by Syria, Russia and the US-led coalition against these groups would continue, according to the statement.
It said armed opposition groups taking part would have to confirm their involvement on 26 February.
The deal also sets up a communications hotline and calls for a working group to monitor ceasefire violations. Violations are to be addressed by the working group with an eye toward restoring compliance and cooling tensions.
In pictures: Russian air strikes in Syria
In pictures: Russian air strikes in Syria
Volunteers from Syria Civil Defence, also known as the White Helmets, help civilians after Russia carried out its first airstrikes in Syria
The aftermath of Russian airstrike in Talbiseh, Syria
Smoke billows from buildings in Talbiseh, in Homs province, western Syria, after airstrikes by Russian warplanes
Russian Air Forces carry out an air strike in the ISIS controlled Al-Raqqah Governorate. Russia's KAB-500s bombs completely destroy the Liwa al-Haqq command unit
Caspian Flotilla of the Russian Navy firing Kalibr cruise missiles against remote Isis targets in Syria
Caspian Flotilla of the Russian Navy firing Kalibr cruise missiles against remote Isis targets in Syria, a thousand kilometres away. The targets include ammunition factories, ammunition and fuel depots, command centres, and training camps
Russia claimed it hit eight Isis targets, including a "terrorist HQ and co-ordination centre" that was completely destroyed
A release from the Russian defence ministry purportedly showing targets in Syria being hit
A video grab taken from the footage made available on the Russian Defence Ministry's official website, purporting to show an airstrike in Syria
Russia launched air strikes in war-torn Syria, its first military engagement outside the former Soviet Union since the occupation of Afghanistan in 1979. Russian warplanes carried out strikes in three Syrian provinces along with regime aircraft as Putin seeks to steal US President Barack Obama's thunder by pushing a rival plan to defeat Isis militants in Syria
The deal also calls for "non-forcible means" to be exhausted before other means are pursued for punishing transgressors.
US Secretary of State John Kerry welcomed the deal, saying: “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."
UN Secretary General Ban Ki-moon also praised the agreement, saying: "Above all, it is a long-awaited signal of hope to the Syrian people that after five years of conflict there may be an end to their suffering in sight."
Speaking to Reuters, Syrian opposition leaders said they were downbeat about the chances of success for the ceasefire.
Bashar al-Zoubi, head of the political office of the Yarmouk Army, a Free Syrian Army group, said he expected Damascus and its Russian allies to continue to attack opposition-held territory on the pretext of fighting the Nusra Front.
"Russia and the regime will target the areas of the revolutionaries on the pretext of the Nusra Front's presence, and you know how mixed those areas are, and if this happens, the truce will collapse," he said.
On 12 February a caesefire was agreed by world powers to come in to effect within a week, but that deadline passed and violence continued.
On Sunday 140 people died in bombings in Homs and Damascus.
More than 250,000 Syrians are believed to have been killed in the conflict since it began in March 2011.
Additional reporting by various agenciesReuse content