US Vice President Joe Biden tried to patch up ties with President Recep Tayyip Erdogan's government this week, but the conflict in Syria has forced Washington into a delicate balancing act.
On the ground, the US strategy relies on using the Kurdish YPG militia backed by American special forces advisors and coalition air power to take the fight to the ISIS terrorist group.
NATO member Turkey is a nominal part of the anti-ISIS coalition, but regards the YPG as part of the same "terrorist" movement as the PKK Kurdish separatist group waging a guerrilla war within its borders.
This week, Ankara sent troops and allied Syrian rebel fighters to seize the Syrian border town of Jarabulus from ISIS group fighters.
But Erdogan also aimed to deny it to the Kurds, who have advanced across the Euphrates River into the region as the dominant faction in the US-backed Syrian Democratic Forces (SDF).
Now Turkey is demanding the Kurds retreat across the river, announcing on Thursday that its military had begun shelling YPG positions north of the town of Manbij, which the Kurds seized this month.
The US dilemma was underlined in a pair of tweets from US diplomat Brett McGurk, President Barack Obama's special envoy coordinating the coalition fighting the Islamic State (ISIS / ISIL) group.
“We support our NATO ally Turkey in protecting its border from ISIL terrorists, and struck ISIL targets near Jarabulus earlier today," he wrote, using the US government's acronym for the IS group.
“We also support the Syrian Democratic Forces which have proven a reliable and extremely capable force in the fight against ISIL," he added, reflecting Washington's reliance on Kurdish manpower; AFP reported.
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