“I don’t want to kill 10m people,” the US president said on Monday.
“I have plans on Afghanistan that if I wanted to win that war, Afghanistan would be wiped off the face of the earth, it would be gone, it would be over in literally 10 days.”
The conflict in Afghanistan has raged for 18 years, with neither the US or the Taliban able to declare victory over the other.
Around 32,000 civilians have been killed in the last decade of the conflict, according the UN, with the number of deaths hitting a record high in 2018.
More than 2,000 US soldiers have also died in the war, which saw US-led forces fighting the Taliban following the 9/11 attacks.
Mr Trump was speaking in the Oval Office, following a meeting with Imran Khan, the prime minister of Pakistan.
His comments come as peace talks between the US and the Taliban progress.
The US leader suggested that Pakistan and Mr Khan could help broker a political settlement to conclude the war, but Afghanistan’s government has reacted with anger following his provocative comments.
“I think Pakistan is going to help us out to extricate ourselves,” the president said.
Mr Khan said negotiators were close to completing a peace deal with the Taliban.
“We hope that in the coming days we will be able to urge the Taliban to speak to the Afghan government and come to a settlement, a political solution,” he said.
On Tuesday officials in Kabul called for Mr Trump to clarify his remarks.
“The Afghan nation has not and will never allow any foreign power to determine its fate,” the country’s government said in a statement.
To the astonishment of watchers of South Asia, Mr Trump claimed he had been asked by India’s prime minister, Narendra Modi, to mediate between the two nations over the disputed territory.
India has consistently rejected external offers of mediation in the past and Pakistan has repeatedly sought third-party help.
The US president’s comments have placed the Indian leader in a difficult diplomatic position.
India later denied Mr Trump’s claims.
Additional reporting by agencies
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