The secretary of state, Rex Tillerson, delivered a speech in which he laid out the reasons for the U.S. "to remain engaged" in Syria. Tillerson identified one key U.S. objective as seeing that "Iranian influence in Syria is diminished, their dreams of a northern arch are denied". He also rejected suggestions that U.S.-backed SDF/YPG forces in northern Syria would constitute a "border force"; that initiative has been criticised by the Assad government, Turkey, and Iran.