The alliance is under its greatest strain in Turkey, which has met US requests to intervene in Kobani on behalf of Kurdish rebels not just with refusal, but with air strikes aimed instead against Kurdish groups in Turkey.
Turkish fighter jets bombarded Kurdistan Workers’ party (PKK) positions in south-eastern Turkey this week for the first time since the start of the peace process between the outlawed group and the Turkish government in 2012.
The attacks on the PKK came in the wake of violent clashes last week between Kurdish factions and security forces in several Turkish cities, as anger grows over perceived government inaction against the Isis attack on Kobani.
According to local media reports, the strikes came in retaliation for armed PKK offensives on several military outposts in the area.
The Turkish chief of general staff said the military “opened fire immediately in retaliation, in the strongest terms” after repeated PKK attacks in the area, and before air strikes were launched.