US wants a unified Syria with no role for Bashar Assad

The US Secretary of State Rex Tillerson said the Assad family's reign is coming to an end as he slammed Iran for taking advantage of the fight against Daesh in the region.

Speaking after a meeting with U.N. special envoy Staffan de Mistura in Geneva, Tillerson said: "The United States wants a whole and unified Syria with no role for Bashar Assad in the government," Tillerson told reporters. "We do not believe there is a future for the Assad regime, the Assad family."

America's top diplomat said that an exit of Assad should be done through the Geneva process led by de Mistura, but that such a departure was not a "prerequisite" for that process to start.

Tillerson also sought to play down any idea that the Assad government's advances might amount to a "triumph" for Iran, which has been a key backer of Assad.

"I see Iran as a hanger-on," Tillerson said. "Iran has not been successful; the Russian government has been more successful. We have had success. I don't think that Iran should be given credit for the defeat of ISIS in Syria."

"The only reason Syrian forces have been successful has been because of the air support they have received from Russia."

America's top diplomat used a stop in Geneva on his way home from a trip to the Middle East and South Asia to meet with de Mistura, before the U.N. envoy was set to address the U.N. Security Council by video conference later in the day.

Russia-backed Assad forces as well as U.S.-backed troops have significantly reduced the territory controlled by Daesh across Syria. The U.S.-backed forces recently ousted Daesh from their so-called capital, Raqqa.