Leave areas east of Euphrates, Khamenei aide tells US

Ali Akbar Velayati, senior foreign policy adviser to Iranian Supreme Leader Ali Khamenei, has called on the U.S. to withdraw from all Syrian territory east of the Euphrates River, according to local media reports.

Velayati made the assertion on Thursday evening at a conference held in the city of Mashad, Iran's Mehr news agency reported.

In a speech delivered before conference attendees, Velayati pointed to alleged plans by the U.S. to break up several countries of the Middle East.

"But the Americans will fail in their attempts to divide Syria," he asserted.

He also told the U.S. to withdraw all military forces from parts of Syria east of the Euphrates -- otherwise, he warned, Iran would "force" them to leave.

In regards to recent allegations that Daesh terrorists had been transferred to Afghanistan from Syria and Iraq, Velayati said: "A Daesh presence in Afghanistan would threaten our 900-kilometer border [with Afghanistan]."

He added: "We cannot allow that."

On the subject of war-torn Yemen, Velayati warned that the country risked becoming "another Vietnam" if Saudi Arabia continued its four-year military campaign against the Shia Houthi militia group.

In 2015, Saudi Arabia and its Sunni-Arab allies launched a massive military campaign in Yemen aimed at crushing Houthi rebels who had overrun much of the country -- including capital Sanaa -- one year earlier.

Riyadh and its allies accuse the Houthis of serving as a proxy force for Shia Iran.