The US and Russia have announced a breakthrough agreement on Syria that foresees a nationwide ceasefire starting early next week.
The ceasefire will be followed by an unlikely new military partnership between the rival governments targeting Islamic State and al Qaida.
At a joint news conference after a marathon day of negotiations, US secretary of state John Kerry said the plan can reduce violence in Syria and lead to a long-sought political transition, ending more than five years of bloodshed.
He called the deal a potential "turning point" in the conflict, if implemented by Syria's Russian-backed government and US-supported rebel groups.
The ceasefire begins at sundown Monday, Mr Kerry said, coinciding with the Muslim Eid al-Adha holiday.
His negotiating partner, Russian foreign minister Sergey Lavrov, confirmed the agreement and said it could help expand the counter-terrorism fight and aid deliveries to Syrian civilians.
He said Syrian president Bashar Assad's government is prepared to comply with the arrangement.