Some of the most senior U.S. diplomats focused on Syria have been abruptly let go from their posts in recent days, according to five people familiar with the matter, in a shake-up that comes as Washington seeks to integrate its Syrian Kurdish allies with the central administration in Damascus.

The diplomats at the Syria Regional Platform (SRP) — the de facto U.S. mission to the country based remotely in Istanbul — all reported to Tom Barrack, the U.S. special envoy for Syria and a longtime adviser and friend of U.S. President Donald Trump.

Appointed in May, Barrack has spearheaded a regional policy shift that backs a unified Syrian state under President Ahmed al-Sharaa, the Islamist leader who swept to power in a lightning advance late last year.