(CNN) President Donald Trump's administration is preparing to announce a long-anticipated drawdown of about 4,000 troops from Afghanistan, a senior administration official confirmed to CNN.

The announcement could come as early as next week, but the official said its timing remains in flux.

Trump previously indicated that he intended to withdraw several thousand troops from Afghanistan, where between 12,000 and 13,000 US troops are currently serving in the 18-year war.

"We're going down to 8,600 and then we make a determination from there as to what happens," Trump told Fox News Radio in August. "We're bringing it down."

The White House and Pentagon did not comment to CNN.

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