The US military expects President Donald Trump to order a further withdrawal of troops from Afghanistan and Iraq, according to defence officials quoted by US media.
Those in Afghanistan will be cut from about 5,000 down to 2,500 by mid-January, officials said. In Iraq they will be reduced from 3,000 to 2,500.
President Trump has previously said he wants "all" troops home by Christmas.
He is refusing to concede the 3 November election to Joe Biden.
The withdrawal should be finished by 15 January, US media reported, just days before Mr Biden's inauguration as president.
But Mr Trump's reported plan is facing rare criticism from a fellow Republican - Senate leader Mitch McConnell, who warned militants would "love" the idea.
Speaking on the floor of the upper chamber on Monday, the Kentucky senator said: "We're playing a limited - limited - but important role in defending American national security and American interests against terrorists who would like nothing more than for the most powerful force for good in the world to simply pick up our ball and go home.
"They would love that."
President Trump has long called for US troops to come home and has criticised US military interventions for being costly and ineffective.
Military leaders were told at the weekend about the planned withdrawals, according to officials quoted by the Associated Press news agency. An executive order is being drawn up but has not yet been sent to commanders, they added.
In September, the Pentagon announced it was to withdraw more than a third of its troops from Iraq within weeks - from about 5,200 to 3,000.
At the time, top US Middle East commander Gen Kenneth McKenzie said those remaining would continue to advise and assist Iraqi security forces in "rooting out the final remnants" of the jihadist group Islamic State (IS).
US-led forces invaded Iraq in 2003 to overthrow President Saddam Hussein, hunting for weapons of mass destruction that turned out not to exist.
US forces have been in Afghanistan since 2001. A US-led coalition ousted the Taliban weeks after the 11 September 2001 attacks in the US by al-Qaeda, which was then based in Afghanistan.
The Taliban regrouped and became an insurgent force that by 2018 was active in more than two-thirds of the country.
The US started withdrawing troops from Afghanistan earlier this year as part of a deal with the Taliban aimed at securing peace in the country.
Drawing back troops was a condition of a historic accord signed by the US and the militants on 29 February.
However, military chiefs, including Gen McKenzie, have warned in the past that peace negotiations between the Taliban and Afghan authorities could be undermined by a hasty US withdrawal.