The ceasefire will go into effect on Sunday, said Russian Foreign Minister

The United States, Russia and Jordan have reached a ceasefire and “de-escalation agreement” in southwestern Syria, one of the combat zones in a six-year-old civil war, U.S. Secretary of State Rex Tillerson said on Friday.

The ceasefire will go into effect on Sunday, Russian Foreign Minister Sergei Lavrov and Jordan's Petra news agency said.

Mr. Tillerson announced the deal after a meeting in the German city of Hamburg between U.S. President Donald Trump and Russian President Vladimir Putin.

He said the area covered by the ceasefire affects Jordan’s security and is a very complicated part of the Syrian battlefield.

“It is (a) well defined agreement on who will secure this area,” he told reporters.

Russia and Iran are the main international backers of Syrian President Bashar al-Assad while Washington supports some of the rebel groups fighting for his ouster.

The Syrian conflict has killed nearly half a million people, according to the Britain-based Syrian Observatory for Human Rights, and forced millions of others to flee the country.

“I think this is our first indication of the U.S. and Russia being able to work together in Syria, and as a result of that we had a very lengthy discussion regarding other areas in Syria that we can continue to work together on to de-escalate the areas,” Mr. Tillerson said.

He had said before going to Hamburg that the United States was prepared to discuss joint efforts with Russia to stabilise Syria, including no-fly zones, ceasefire observers and coordinated deliveries of humanitarian assistance.

The United States and Russia held secret talks on creating a de-escalation zone in southern Syria, Western diplomats and regional officials said in early June.

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The proposed zone was in Deraa province, on the border with Jordan, and Quneitra, which borders the Israeli-occupied Golan Heights, they said.

Backed by Russian air power, Mr.Assad has regained ground in the last year that he lost to the mostly Sunni Muslim rebels earlier in the conflict.

The Syrian army has in recent months escalated its strikes in the southwestern city of Deraa in a campaign to reach the border with Jordan and wrest full control of the city.

The army said on Monday it would suspend combat operations in southern Syria, but rebels said the military had violated the ceasefire by striking areas under their control.