US President Barack Obama will host a summit in New York next month of leaders of the international coalition fighting Islamic State jihadists in Syria and Iraq, diplomats said.

The summit on countering violent extremism on September 29 comes one year after Obama vowed to crush IS during his United Nations speech.

Since then, the jihadists have captured territory in Syria and Iraq and gained a foothold in Libya, Yemen and elsewhere in the Middle East, with alliances as far afield as Nigeria’s Boko Haram.

On Wednesday, IS released a picture on Twitter of a Croatian hostage abducted in Egypt, who apparently was the latest victim of the group’s horrific beheadings.

The United States last year assembled a coalition of 50-plus countries to beat back Islamic State, which declared a caliphate in June 2014 after seizing the Iraqi city of Mosul.

Diplomats said the summit, to be held on the sidelines of the annual UN General Assembly meeting, will allow leaders to take stock and chart a way forward in the campaign to defeat Islamic State.

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