The Syrian Observatory for Human Rights announced that Syrian Arab rebel groups and Kurds militias backed by the US forces advanced towards Tishrin Dam in northern Syria which is controlled by Daesh fighters, Al-Arabiya news channel reported on Friday.
According to the observatory, the so-called Democratic Forces of Syria, which include the powerful Kurdish militants and an Arab tribal alliance, advanced to nearly 20 km towards the dam.
The dam is one of three major dams on the Euphrates River.
Syria's bloody conflict has killed more than a quarter of a million people since it started nearly five years ago, and displaced half the Middle Eastern country's pre-war population of 23 million.
Last Friday, the UN Security Council unanimously approved a resolution endorsing a peace process for Syria, including a cease-fire and talks between the Syrian government and opposition.