Trump, who is seeking re-election next month, has made troops’ pullout from the cornerstone of his foreign policy.

All US troops in Afghanistan should be “home by Christmas”, President Donald Trump said, just hours after his national security adviser said Washington would reduce its forces in Afghanistan to 2,500 by early next year.

A landmark deal between the United States and the Taliban in February said foreign forces would leave Afghanistan by May 2021 in exchange for security guarantees by the Afghan armed group.

Also, as a result of the deal, negotiations between the Afghan government and the Taliban started last month in the Qatari capital Doha to achieve lasting peace in the war-torn country. Rival negotiators have been pushing for the reduction of violence and a possible new power-sharing agreement in Kabul.

Trump and other officials have said the US will decrease its troops between 4,000 and 5,000 in Afghanistan by November. Beyond that, officials have said a reduction will depend on conditions in Afghanistan.

On Twitter, Trump said: “We should have the small remaining number of our BRAVE Men and Women serving in Afghanistan home by Christmas!”

It was unclear whether Trump was giving an order or verbalising a long-held aspiration.

Trump, who is seeking re-election next month, has made troops pullout from “ridiculous endless wars” the cornerstone of his foreign policy, even though thousands of troops remain in Iraq, Syria and Afghanistan.

‘Slow progress’

Just hours before Trump’s tweet, NSA Robert O’Brien said the US had less than 5,000 troops in Afghanistan currently and would go down to 2,500 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 the White House did not immediately respond to a request for comment.

The White House’s plan for the withdrawal will almost certainly be subject to review should Trump lose his bid for a second term in the November 3 election.

Trump’s comments could further weaken the Afghan government’s leverage during negotiations with the Taliban.

While the talks have been taking place in Qatar’s capital, many Afghan soldiers and Taliban fighters have been killed in clashes. Dozens of civilians have also died in recent weeks.

Testifying before a House of Representatives committee last month, Special Envoy Zalmay Khalilzad said once the number of US troops reached 4,500, the administration “would do an evaluation of ties and actions that we have taken and make decisions on that”.

About 2,400 US service members have been killed in the Afghan conflict and thousands of others wounded.

Wednesday also marks 19 years since the US invaded Afghanistan after blaming the then-Taliban rulers for harbouring al-Qaeda leaders, including Osama bin Laden. Al-Qaeda was accused of plotting the 9/11 attacks.