US troops in Afghanistan and Iraq would be cut significantly by January 2021. Acting Secretary of Defense Christopher Miller announced Tuesday that the withdrawal would come just days before President-elect Joe Biden takes office.

Currently there are approximately 4,500 US troops in Afghanistan and in Iraq.

"By January 15, 2021, our forces, their size in Afghanistan will be 2,500 troops. Our force size in Iraq will also be 2,500 by that same date." Christopher Miller, the acting US defense secretary announced.

Shortly after the announcement, National security adviser Robert O'Brien told reporters  "by May, it is President Trump's hope that they will all come home safely, and in their entirety".

Anticipating the move, Senate Majority leader Mitch McConnell, normally a Trump "supporter", had been highly critical.

"A rapid withdrawal of US forces from Afghanistan now would hurt our allies and delight the people who wish us harm us. .... It would be reminiscent of the humiliating American departure from Saigon in 1975. " McConnell told Congress.

The announcement has also been met with dismay and warnings from allies.

Nato's chief said there would be a "high price" if US and allied forces leave Afghanistan too quickly adding the country risked once again becoming a platform for international militants to organise attacks.

The pullout falls short of Trump's promise to bring all troops home by Christmas, but it will come into effect in his final days in office - enabling him to leave claiming he fulfilled an original campaign pledge.