US troops will start withdrawing from Afghanistan immediately, US President Donald Trump says, following the signing a peace deal with the Taliban.
The historic deal if upheld could bring an end to America's 'longest-fought war'.
The 'Agreement for Bringing Peace to Afghanistan' was signed in Doha, Qatar, on Saturday and witnessed by US Secretary of State Mike Pompeo.
Mr Trump on Sunday told reporters that American troops would begin leaving Afghanistan.
"Today. They will start immediately," Mr Trump said at the White House, in response to a question about a withdrawal.
"No one should be criticising this deal, after 19 years," he said, referring to the length of the US involvement in the conflict in Afghanistan.
Acknowledging a military stalemate after nearly two decades of conflict, the US signed the peace agreement with the Taliban to end America's longest war and bring US troops home after they invaded in the wake of the September 11, 2001, terrorist attacks.
The historic deal, signed by chief negotiators from the two sides and witnessed by Secretary of State Mike Pompeo, could see the withdrawal of all American and allied forces in the next 14 months and allow Mr Trump to keep a key campaign pledge to extract the US from "endless wars."
But it could also easily unravel, particularly if the Taliban fail to meet their commitments.
At the White House, Mr Trump told reporters the US deserves credit for having helped Afghanistan take a step toward peace. He spoke cautiously of the deal's prospects for success and cautioned the Taliban against violating their commitments.
"We think we'll be successful in the end," he said, referring to all-Afghan peace talks and a final US exit. He said he will be "meeting personally with Taliban leaders in the not-too-distant future," and described the group as "tired of war."
He did not say where or why he plans to meet with Taliban leaders. He said he thinks they are serious about the deal they signed but warned that if it fails, the US could restart combat.
"If bad things happen, we'll go back" in with military firepower, Mr Trump said.
Mr Pompeo was similarly cautious.
"Today, we are realistic. We are seizing the best opportunity for peace in a generation," Mr Pompeo said in the Qatari capital of Doha.
"Today, we are restrained. We recognise that America shouldn't fight in perpetuity in the graveyard of empires if we can help Afghans forge peace."
Under the agreement, the US would draw its forces down to 8600 from 13,000 in the next three-to-four months, with the remaining US forces withdrawing in 14 months.
The complete pullout would depend on the Taliban meeting their commitments to prevent terrorism, including specific obligations to renounce al-Qaeda and prevent that group or others from using Afghan soil to plot attacks on the US or its allies.
The deal sets the stage for intra-Afghan peace talks to begin around March 10, with the aim of negotiating a permanent cease-fire and a power-sharing agreement between rival Afghan groups.
It's perhaps the most complicated and difficult phase of the plan. It does not, however, tie America's withdrawal to any specific outcome from the all Afghan talks, according to US officials.
Mr Pompeo said that "the chapter of American history on the Taliban is written in blood" and stressed that while the road ahead would be difficult, the deal represented "the best opportunity for peace in a generation."