The United States and Russia have reached agreement on a ceasefire in southwest Syria, three US officials said as President Donald Trump held his first meeting with Russian President Vladimir Putin.

The deal marks a new level of involvement for the US in trying to resolve Syria's civil war. Although details about the agreement and how it will be implemented weren't immediately available, the cease-fire is set to take effect Sunday at noon Damascus time, said the officials, who weren't authorised to discuss the cease-fire publicly and spoke on condition of anonymity.

Jordan and Israel also are part of the agreement, one of the officials said. The two US allies both share a border with the southern part of Syria and have been concerned about violence from Syria's civil war spilling over the border.

The deal is separate from “de-escalation zones” that were to be created under a deal brokered by Russia, Turkey and Iran earlier this year. The US was not a part of that deal. Follow-up talks this week in Kazakhstan to finalise a cease-fire in those zones failed to reach agreement.

The US and Russia have been backing opposing sides in Syria's war, with Moscow supporting Syrian President Bashar al-Assad and Washington supporting rebels who have been fighting Assad. Both the US and Russia oppose Isis group in Syria.

The US has been wary of letting Iran gain influence in Syria — a concern shared by Israel and Jordan, neither of which wants Iranian-aligned troops amassing near their territories. A US-brokered deal could help the Trump administration retain more of a say over who fills the vacuum left behind as Isis is removed from additional territory in Syria.

Aleppo before the Syrian Civil War Show all 12 1 /12 Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A man crosses a street in Aleppo, December 12, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A vendor sits inside an antique shop in al-Jdeideh neighbourhood, in the Old City of Aleppo, December 12, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A view shows part of Aleppo's historic citadel, overlooking Aleppo city, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A view shows part of Aleppo's historic citadel, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War Visitors walk inside Aleppo's Umayyad mosque, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War People walk inside the Khan al-Shounah market, in the Old City of Aleppo, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A man walks past shops in al-Jdeideh neighbourhood, in the Old City of Aleppo, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War People walk along an alley in al-Jdeideh neighbourhood, in the Old City of Aleppo, Syria Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War Visitors tour Aleppo's historic citadel, Syria December 11, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A general view shows the Old City of Aleppo as seen from Aleppo's historic citadel, Syria December 11, 2009 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War People walk near Aleppo's Bab al-Faraj Clock Tower, Syria October 6, 2010 Reuters Aleppo before the Syrian Civil War Aleppo before the Syrian Civil War A man stands inside Aleppo's historic citadel, overlooking Aleppo city, Syria December 11, 2009 Reuters

Though US and Russian officials had been discussing a potential deal for some time, it didn't reach fruition until the run-up to Mr Trump's meeting with Putin on the sidelines of the G20 economic summit in Germany, officials said.

Before Mr Trump's meeting with Mr Putin — his first with the Russian leader — Secretary of State Rex Tillerson signalled that Syria's civil war would be high on the agenda. Mr Tillerson said in a statement before departing for Germany for the meeting that the U.S. remained open to cooperating with Russia through “joint mechanisms” to lower violence in Syria, potentially including no-fly zones.

“If our two countries work together to establish stability on the ground, it will lay a foundation for progress on the settlement of Syria's political future,” Mr Tillerson said on Wednesday.