All US troops in Afghanistan should be home by Christmas, President Donald Trump says.
He made the announcement on Wednesday, just hours after his national security adviser said Washington would reduce its forces in Afghanistan to 2500 by early next year.
A landmark deal between the United States and the Taliban in February determined foreign forces would leave Afghanistan by May 2021 in exchange for counterterrorism guarantees from the Taliban.
It also agreed to negotiate a permanent ceasefire and a power-sharing formula with the Afghan government.
Trump and other officials have said the United States will go down to between 4000 and 5000 troops in Afghanistan around November.
Beyond that, officials have said a reduction will depend on conditions in Afghanistan.
"We should have the small remaining number of our BRAVE Men and Women serving in Afghanistan home by Christmas!" Trump said on Twitter.
It was unclear whether he was giving an order or verbalising an aspiration.
Trump has made walking away from "ridiculous endless wars" the cornerstone of his foreign policy, even though thousands of troops remain in Iraq, Syria and Afghanistan.
The Taliban, fighting to expel foreign forces and re-establish their Islamic state since their ouster in 2001, welcomed Trump's comments.
His statement was "a positive step towards the implementation of the Doha agreement", Taliban spokesman Mohammad Naeem said in a statement, referring to the February pact signed in the Qatari capital.
The US-backed Afghan government did not immediately respond to requests for comment but officials have warned against a hasty withdrawal of foreign forces.
Trump's comments could further weaken the Afghan government's leverage during negotiations with the Taliban on a ceasefire and power-sharing taking place in Qatar.
Just hours before Trump's tweet, national security adviser Robert O'Brien said the United States had less than 5000 troops in Afghanistan currently and would go down to 2500 by early next year.
"Ultimately, the Afghans themselves are going to have to work out an accord, a peace agreement. ... It's going to be slow progress, it's going to be hard progress but we think it's a necessary step - we think Americans need to come home," O'Brien told an event at the University of Nevada, Las Vegas.
The National Security Council and White House did not immediately respond to a request for comment.