ANKARA/ISTANBUL (Reuters) - Turkey’s military struck the Syrian-Iraqi border to prevent Kurdish forces using the route to reinforce northeast Syria, as Ankara prepared to attack there following a surprise U.S. troop pullback, Turkish officials told Reuters on Tuesday.

Turkey says it is ready to advance into northeast Syria now that the United States has begun withdrawing troops from the Turkey-Syria frontier in an abrupt policy shift by U.S. President Donald Trump widely criticized in Washington as a betrayal of America’s allies, the Kurds.

The U.S. move will leave Kurdish-led forces long allied to Washington vulnerable to attack by the Turkish Armed Forces (TSK), which brands them terrorists because of their links to Kurdish militants who have waged a long insurgency in Turkey.

Giving details of the overnight strike, a security official said one of the main goals was to cut off a transit route between Iraq and Syria often used by Kurdish armed groups “before the operation in Syria”.