The Trump administration is planning to withdraw thousands of troops from Afghanistan, US media say.
Reports, citing unnamed officials, say about 7,000 troops – roughly half the remaining US military presence in the country – could go home within months.
The reports come a day after the president announced the country’s military withdrawal from Syria.
Earlier on Thursday, Mr Trump’s defence secretary, Jim Mattis, announced his resignation from his post.
In his letter of departure, Gen Mattis mentioned his diverging views with the president, but did not cite troops withdrawals directly.
Before his election, Mr Trump repeatedly publicly advocated leaving Afghanistan – where US forces have been since 2001.
However, last year he indicated he would keep boots on the ground in the country indefinitely to prevent the country’s collapse amid a Taliban resurgence.
American-led combat operations against the group officially ended in 2014, but in the years since the group’s power and reach has soared.
In September 2017 Mr Trump announced the US would send 3,000 extra troops to the country amid a shift of strategy.
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Reports about the sharp reduction of personnel emerged on Thursday, but have not been confirmed by US defence officials.
The Washington Post reports the potential move is being met with opposition by some of Mr Trump’s senior cabinet officials including outgoing White House Chief of Staff John Kelly and White House national security adviser John Bolton.
Republican senator Lindsey Graham tweeted that any withdrawal of troops would be a “high risk strategy” which could reverse US progress in the region and pave the way toward a “second 9/11”.
He had earlier spoken out against the Syria withdrawal, which he described as a “huge Obama-like mistake”.
Wednesday’s announcement on Syria was also met with criticism from US allies and coalition partners.
A statement from a Kurdish-led alliance warned the move could create a vacuum whereby the depleted Islamic State (IS) group could “revive itself”.