German Chancellor Angela Merkel warned Saturday that a hasty US pullout from Syria runs the risk of strengthening the roles of Russia and Iran in the Middle East. ISIS group fighters have been boxed into a scrap of land in the battle for their last remaining territory in northeastern Syria and their final defeat is expected imminently. Once they are defeated, US forces are set to soon withdraw after President Donald Trump in December announced the pullout of around 2,000 troops. Washington says it will maintain a presence in the region, with Vice-President Mike Pence pledging to carry on the fight. "The United States will continue to work with all our allies to hunt down the remnants of ISIS wherever and whenever they rear their ugly heads," Pence said. But Washington is struggling to convince allies to stay on in Syria after it leaves and Merkel warned of the risks of leaving a vacuum in the region. "Is it a good idea for the Americans to suddenly and quickly withdraw from Syria? Or will it once more strengthen the capacity of Iran and Russia to exert their influence?" Merkel said at the Munich Security Conference. Pentagon chief Patrick Shanahan on Friday pledged ongoing backing for the fight against ISIS -- but kept allies guessing as to how that would be achieved once US forces pull out. Belgian Foreign Minister Didier Reynders said the US had told partners in the global anti-ISIS coalition that its soldiers would leave in "weeks rather than months". The decision has stunned allies including France, which contributes artillery and about 1,200 troops in the region, including soldiers who train Iraqi forces. French Foreign Minister Jean-Yves Le Drian asked why the US would create a vacuum in Syria that could benefit its enemy Iran, calling the approach a "mystery". And the US has won no solid pledges of support for a proposed observer force to stay on in northeast Syria when the US pulls out to ensure the safety of Syrian Kurdish fighters. A French government source criticized the Trump administrations approach to the withdrawal as "were leaving, youre staying". "Theyre trying to manage the consequences of a hasty decision and making us carry the responsibility," the source said, adding that coalition members were united in rejecting the idea of staying on in Syria when the US leaves.