WASHINGTON: The United States will temporarily deploy extra troops to Afghanistan to protect international forces as they withdraw, commander of the US military in the Middle East General Kenneth McKenzie said Thursday.

McKenzie repeated US military concerns that the withdrawal could allow the Taliban to advance, after President Joe Biden last week announced all US forces would pull out before this year's 20th anniversary of the September 11 attacks.

"We will bring additional resources in, in order to protect the force as it comes out," McKenzie told a US Senate hearing, giving no further details.

"That's normal in any kind of disengagement. I'm confident that... we will be able to extract ourselves."

McKenzie did not talk about numbers when asked about the size of the withdrawal reinforcement at later at a press conference, saying that the plans are currently being worked on.

Some 2,500 US troops, plus 16,000 civilian contractors and their equipment, must be evacuated from the country, along with some 7,000 NATO soldiers who depend on the US for transport.

The logistical operation will take at least three months to be completed safely, according to the US military.