The president’s remark to reporters at the White House on Monday suggested he sees no point in resuming a nearly year-long effort to reach a political settlement with the Taliban, whose protection of al Qaida extremists in Afghanistan prompted the US to invade after the 9/11 attacks.
Asked about the peace talks, he said: “They’re dead. They’re dead. As far as I’m concerned, they’re dead.”
Mr Trump said his administration is “looking at” whether to proceed with troop reductions that had been one element of the preliminary deal with the Taliban struck by presidential envoy Zalmay Khalilzad.
“We’d like to get out, but we’ll get out at the right time,” the president said.
What had seemed like a potential deal to end America’s longest war unravelled, with Mr Trump and the Taliban blaming each other for the collapse of nearly a year of US-Taliban negotiations in Doha, Qatar.
The insurgents are now promising more bloodshed, and American advocates of withdrawing from the battlefield questioned whether Mr Trump’s decision to cancel what he called plans for a secret meeting with Taliban and Afghan leaders at the Camp David presidential retreat over the weekend had poisoned prospects for peace.
Mr Trump has been talking of a need to withdraw US troops from the “endless war” in Afghanistan since his 2016 presidential campaign.
In a tweet on Monday he said: “We have been serving as policemen in Afghanistan, and that was not meant to be the job of our Great Soldiers, the finest on earth.”
He added, without explanation: “Over the last four days, we have been hitting our Enemy harder than at any time in the last ten years.”
There has been no evidence of a major US military escalation.
Secretary of state Mike Pompeo defended Mr Trump’s weekend moves.
“When the Taliban tried to gain negotiating advantage by conducting terror attacks inside of the country, President Trump made the right decision to say that’s not going to work,” Mr Pompeo said on Sunday.
Mr Trump said he called off negotiations because of a recent Taliban bombing in Kabul that killed a US service member, even though nine other Americans have died since June 25 in Taliban-orchestrated violence.
But the emerging agreement had started unravelling days earlier after Afghan President Ashraf Ghani postponed his trip to Washington and the Taliban refused to travel to the US before a deal was signed, according to a former senior Afghan official.
At the Pentagon, spokesman Jonathan Hoffman declined to comment on the outlook for the administration’s plan to reduce the US troop level in Afghanistan from up to 14,000 to 8,600.