The US has installed a number of observation posts overlooking the Turkish border in Kurdish-controlled parts of northern Syria, in a move that has antagonised Washington's Nato ally, as it prepares for an offensive on its southern border.
"The observation posts are being established in areas along the border where there is a potential for clashes between Turkey and Kurdish forces," Nouri Mahmoud, a spokesperson for the People's Protection Units (YPG), told The National on Tuesday.
He refused to disclose how many observation posts the US has established, but said the regions of Tel Abyad, Ras Al Ain and Kobane, were among the places were observation posts were "deemed necessary".
Iraqi Kurdish outlet Rudaw reported on Friday that US forces have established at least five posts along the border.
Col. Sean Ryan, a spokesman for the US-led coalition said in an emailed statement that US forces are securing locations for manned observation posts "to support security and stability on the border, and improve the Coalition's situational awareness to enable the continued fight against ISIS."
"The goal is keeping all parties focused on ensuring the enduring defeat of ISIS, our common enemy that still poses a significant threat to Syria, Iraq, Turkey and our partners around the world," he added.
The spokesman said that the US-led coalition does not define an observation post as a "permanent structure by military means," clarifying that the number of posts and their location could change at any moment, depending on developments.
Spokesman for the Kurdish-led Syrian Democratic Forces Mustafa Bali told The National that their purpose was to "deliver a message to Turkey that the coalition and its Kurdish partners in Syria do not pose a threat to Turkey's security."
Turkish Vice President Fuat Oktay called on the US on Monday to act as a partner that respects Ankara's operations against Kurdish rivals stationed across the border.
"As Turkey, our expectation from the US is for it to act according to the spirit of the alliance in every single area," Mr Oktay was quoted as saying by Turkey's state-run Anadolu Agency. "We also want to see an America that respects Turkey's fight against terrorist organisations," he said, adding that an operation against Kurdish groups positioned in areas adjacent to Turkey's southern border is "on the agenda."
Earlier on Friday, Turkey's Defence Minister Hulusi Akar told US Syria envoy Jim Jeffrey that the US should stop building posts along the border.
“The US should cut ties with the YPG, which is no different from the PKK," Mr Akar told the US envoy, according to Turkey's state-run Anadolu Agency, referring to the Kurdistan Workers' Party – a militia waging a decades-long insurgency against the Turkish government.
The group is designated a terrorist organisation by Turkey, the United States and the European Union and works closely with the YPG.
"The US should also call off its plan to set up observation points in northern Syria,” Mr Akar said.
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Ankara has has previously expressed anger at US support for the YPG.
“During our talks with both political and civilian interlocutors we repeatedly expressed our unease in various ways,” said Mr Akar last month. “I think actions like this will make the complicated situation in the region even more complicated.”
President Recept Tayyip Erdogan has sent troops into northern Syria to attack Kurdish positions before and is reportedly angered by the observation posts.
According US Defense Secretary James Mattis, the posts are there to warn its Nato ally of any threats to Turkish territory. Turkish leaders see it as a plan to protect the Kurds.
US officials have warned that extending Turkish military action east along the Syrian frontier would raise the chances of a direct confrontation with American troops. It would also damage international efforts to prevent an ISIS resurgence by drawing Kurds away from a battle they fought for years to win, they say. Mr Erdogan rejects those arguments.
His aim instead is to dislodge the YPG from the stretch of land running from Manbij to the eastern border with Iraq.
The Trump administration hopes that the US-backed fight against ISIS in its last foothold in northeastern Syria will end within months. But a top US diplomat recently said American forces will remain to ensure the “enduring defeat” of the militant group.
Syria's long-oppressed Kurdish minority has established a semi-autonomous region in the north of the country, which has been wracked by conflict since 2011.
Turkey refuses to recognise the territory on its border, fearing it will stoke the separatist ambitions of Kurds in its own country.