Turkish President Recep Tayyip Erdogan refused to meet with National Security Adviser John Bolton on Tuesday, saying Bolton had made a “serious mistake” in introducing new conditions for the U.S. military withdrawal from Syria. Before he arrived in Ankara, Bolton said that no U.S. troops would leave Syria until Turkey agreed to not attack the Syrian Kurds. The U.S. has backed the Kurds in the fight against ISIS. But during a speech in parliament, Erdogan—who sees the YPG Kurdish militia as a terrorist organization—said Turkey would never compromise on the Kurdish issue. Bolton ended his visit to Turkey after two hours of discussions with officials Tuesday, but without meeting Erdogan. The Turkish president reportedly called Bolton’s Turkish counterpart, Ibrahim Kalın, and asked him to send his regards to Bolton, but said he was too busy to meet him in person. Administration officials told NBC News that a meeting between Erdogan and Bolton was expected. Erdogan later said Turkey wants U.S. bases in Syria emptied and handed over, according to Reuters, and that no pledge had been made to protect the Kurdish militia.