US Defence Secretary Patrick Shanahan gives a press conference following the North Atlantic Council of Defence Ministers, at the NATO headquarters in Brussels, on February 14, 2019. (File photo: VCG)

Pentagon chief Patrick Shanahan on Friday pledged ongoing support for the fight against Islamic State after the jihadists are finally ousted from Syria but kept allies guessing as to how once US forces pull out.

"Together, we have eliminated the group's hold over 99 percent of the territory it once claimed as part of its so-called caliphate," he said after meeting allies in the anti-IS coalition.

"While the time for US troops on the ground in northeast Syria winds down, the United States remains committed to our coalition's cause: the permanent defeat of ISIS, both in the Middle East and beyond," he said after talks on the sidelines of the Munich Security Conference.

He said the US would "maintain our counterterrorism capabilities in the region" and "continue to support our local partners' ability to stand up to the remnants of ISIS" -- but gave no details about how this would be done.

In recent days, IS fighters have been cornered by a US-backed Arab-Kurdish militia in a last battle over the remaining patch of territory the militants control in northeastern Syria.

With defeat of IS's self-declared "caliphate" imminent, American troops are set to withdraw from Kurdish-controlled areas.

US President Donald Trump in December announced the pullout of around 2,000 US troops, stunning allies including France and Britain who warned the fight against jihadists was not finished.