U.S. Special Representative for Syria Engagement James Jeffrey will visit Turkey on Wednesday, reports said Monday.

Jeffrey, who also serves as the U.S. special envoy for the Global Coalition to Defeat Daesh, was previously in Ankara as part of a high-level U.S. delegation led by Vice President Mike Pence to discuss Turkey's anti-terror operation in northeastern Syria.

Jeffrey told a news briefing in January that the Syrian regime and Russian warplanes had hit Idlib with 200 airstrikes "mainly against civilians" in the past three days.

He said the assault had set "700,000 people who are already internally displaced on the move once again toward the Turkish border, which will then create an international crisis."

President Recep Tayyip Erdoğan said Wednesday that Ankara was losing patience with the Idlib assault and would retaliate against any attack on its 12 observation posts in the area.