US President Donald Trump is weighing up whether to send more troops to Afghanistan as officials say the political and security situation will "almost certainly" continue to worsen in the war-torn country.

Afghan Voice Agency(AVA), Trump’s advisers are reportedly urging him to allow some 3,000 to 5,000 additional troops to be sent to Afghanistan, adding to the 8,400 already stationed in the country.

Trump is expected to make the decision later this month during his travel to NATO in Brussels, and Pentagon chief Jim Mattis said he would give his own recommendation "very shortly."

According to The New York Times, Trump is close to signing off on the recommendation, which is the result of a broad review by the Pentagon, the State Department, intelligence community and other government agencies on the Afghan war.