US intelligence chief: IS remains a threat
Dan Coats told a gathering of world leaders, diplomats and defence officials on Saturday that defeating the extremist group was like "killing an octopus".
It's more than just a terrorist organisation. It is an ideology and perhaps a theology, and the combination of ideology and theology outlasts defeats on the battlefield," Coats said.
He added it is not currently clear whether "we've done enough to keep ISIS from reconstituting, or if we're just in a moment of pause while they're regrouping," using an alternative acronym for the militant group.
Coats said the current assessment is it "will remain a threat".
Iraq declared victory against IS in December, more than three years after the extremist group seized a third of its territory and swathes of neighbouring Syria, declaring a "caliphate" ruling over millions of people.
As the fight against the IS group nears its end, with the extremist group losing large swathes of land, the group's territory is now reduced to a small strip of the Euphrates and small areas of Syria and Iraq.
There are less than 1,000 IS fighters estimated remaining in Iraq and Syria.
Earlier in the week, the United States urged allies to remain focused on their fight against the Islamic State group, highlighting that Turkey's military offensive, operation Olive Branch in the northern Syrian city of Afrin, had "detracted" from the anti-IS fight.