The Kurdish authorities in northeast Syria said Tuesday their forces had started to withdraw from outposts along the Turkish border after a US-Turkish deal for a buffer zone there. They said work had begun Saturday on "the first practical steps -- in the Ras al-Ain area -- in removing some earth mounds and withdrawing a group of (Kurdish) Peoples Protection Units and heavy weapons". On Monday, they repeated the same steps in Tal Abyad, "showing the seriousness of our commitment to current understandings" on the buffer zone, the semi-autonomous Kurdish administration said in a statement. The so-called "safe zone" agreed by Washington and Ankara earlier this month aims to create a buffer between the Turkish border and Syrian areas controlled by the Kurdish Peoples Protection Units (YPG), a group Ankara sees as "terrorists". Details of the safe zone are currently hazy, and no final date has been set for when it would be established. But on Monday, Turkeys President Recep Tayyip Erdogan said Turkish troops would soon enter northeast Syria. "Our armed drones, drones, and helicopters are in the region," he said. "We expect our ground troops to enter the region very soon," he told supporters in eastern Turkey. On Saturday, Turkish Defence Minister Hulusi Akar said a US-Turkey operations center aimed at creating the buffer area was at "full capacity". He said the first joint helicopter flight took place on Saturday afternoon. Mazlum Abdi, the chief of the Kurdish-led Syrian Democratic Forces, on Saturday said his forces would support the implementation of the US-Turkey deal. Turkey has repeatedly threatened to attack Kurdish-held areas in northeast Syria. Ankara considers the YPG, which forms the backbone of the SDF, to be an extension the outlawed Kurdistan Workers Party (PKK) -- a group that has fought a bloody insurgency inside Turkey for 35 years. The "safe zone" was initially suggested by Washington to dissuade Ankara from carrying out another cross-border attack, after previous offensives in 2016 and 2018. The YPG has been a key partner to Washington in the fight against ISIS in Syria. But as the fight against ISIS winds down in the region, the prospect of a US military withdrawal has stoked Kurdish fears of another Turkish attack. Syrias Kurds have largely stayed out of the countrys eight-year civil war, instead building their own autonomous institutions in areas they control.