Trump’s comment follows similar remarks by US Secretary of State Mike Pompeo and US Ambassador to the United Nations Nikki Haley.
Tehran is set to host an upcoming summit with Russian and Turkish leaders over the situation in Syria on September 7.
Upon arrival in the Syrian capital earlier on Monday, Zarif asserted that “Terrorists operating in the remaining parts of Idlib must be cleansed, and the region be returned to the people of Syria,”
Last week, Iranian Defense Minister Amir Hatami visited Damascus, where he signed a “defense and technical agreement.”
The Syrian army, meanwhile, is gearing up for a major offensive to retake the last terrorist stronghold, but it is facing threats of being hit by the US and its allies.