Donald Trump appeared to backpedal from a green light for Turkey to attack U.S.-allied Kurdish forces in northern Syria, warning Ankara in a tweet that he would “totally destroy and obliterate” the country’s economy if takes unspecified “off limits” actions.

The president has drawn fierce criticism from congressional allies for a White House statement late Sunday that said the U.S. wouldn’t stand in the way of a Turkish incursion into northern Syria. The announcement, which followed a call with Turkish President Recep Tayyip Erdogan, marked an abrupt change in U.S. posture.

Senator Lindsey Graham, a South Carolina Republican who is normally a close Trump ally, said he would introduce bipartisan legislation to sanction Turkey if it invades Syria and suspend it from NATO if it attacks Kurdish forces.