Ankara, Turkey -- U.S. National Security Adviser John Bolton arrived Monday in Turkey for negotiations on the fate of American-allied Kurdish fighters, who said they were unclear what to make of his recent comments about U.S. plans to withdraw troops from Syria. The Kurdish militiamen and women were central to the U.S. military's fight against ISIS in Syria, and many saw President Trump's recent announcement of a pull-out as potentially putting those allies at risk.

The president's sudden announcement that all 2,000 U.S. troops in Syria were coming home -- the timetable for which Bolton has since slowed down and qualified -- raised fears that Turkey could launch an assault on the Kurdish fighters, whom the Turks consider terrorists. Turkey considers the Syrian Kurdish People's Protection Units, or YPG, as an extension of a Kurdish insurgency within its own borders.

Bolton will seek assurances from Turkey, a NATO ally, that it won't attack the Kurds when the U.S. withdraws troops from northeastern Syria. Monday's visit comes just one day after Bolton said such guarantees were a "condition" of the pullout President Trump ordered last month.

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Bolton, on a visit to Israel Sunday, said U.S. troops would not leave northeastern Syria until ISIS militants are defeated and the Kurdish fighters are protected. The comments appeared to put the brakes on the withdrawal announced by Mr. Trump in December, initially expected to be completed within weeks.

CBS News national security correspondent David Martin reported on Monday that the U.S. military was continuing to conduct air and artillery strikes against ISIS targets in Syria, along with allies.

Bolton, who has said that any Turkish offensive against the U.S.-allied Kurds would be unacceptable, was expected to meet Tuesday with Turkish officials including President Recep Tayyip Erdogan.

Allied Kurds want clarification of U.S. policy

The Kurds themselves said Monday that they were awaiting clarification from the U.S. over America's plans to pull out troops from Syria following Bolton's remarks over the weekend.

Speaking to The Associated Press from northern Syria Monday, Badran Ciya Kurd said the Kurds had not been informed of any change in the U.S. position and were in the dark about Bolton's the latest comments.

"We have not been formally or directly notified, all what we heard were media statements," he said.

The changing message from Washington has been troubling for the Kurds, who have been America's only real combat partners on the ground in Syria in the fight against ISIS.

Mr. Trump's decision last month drew widespread criticism from allies, led to the resignation of U.S. Defense Secretary Jim Mattis and raised fears that Turkey might make good on its threat to launch an offensive against the Kurdish fighters in northern Syria.

CBS News' Martin has reported that the Turkish military is massing forces along its southern border with Syria.