The deal marks a new level of involvement for the U.S. 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 authorized 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 U.S. 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 U.S. was not a part of that deal. Follow-up talks this week in Kazakhstan to finalize a cease-fire in those zones failed to reach agreement.