Speaking during an interview on Fox News Radio, Trump said the United States would decrease its presence to 8,600 troops and then "make a determination" as to what further steps to take.
"We're not fighting a war over there -- we're just policemen," Trump said. "We could win that war so fast if I wanted to kill 10 million people ... but I don't. I'm not looking to kill a big portion of that country."
Roughly 14,000 troops are stationed in Afghanistan, advising and assisting Afghan forces and conducting counterterrorism operations against groups such as the Islamic State and al-Qaida.
Trump's comments come after Taliban spokesman Suhail Shaheen said that the two sides were close to a deal that would have the United States and foreign forces withdraw from Afghanistan in exchange for a commitment from the Taliban to not use the nation to launch terrorist attacks against the United States.
Full removal of troops from Afghanistan has faced criticism from some opponents who fear such a withdrawal could allow for a resurgence of terrorist groups in the country.
"We may be in such a rush to remove our forces that we find ourselves on the cusp of a strategic blunder," Sen. Lindsey Graham, R-S.C., wrote in a Washington Post op-ed on Wednesday. "Any deal that calls for withdrawing our forces completely from Afghanistan is a bad deal for the United States."