Dan Driscoll's departure was announced by the White House. (AP: Karl DeBlaker)
US Army Secretary Dan Driscoll has stepped down after 18 months on the job.
Mr Driscoll's departure, the latest in a series of Pentagon shake-ups, reportedly followed tensions with Defense Secretary Pete Hegseth.
Former US Navy Secretary John Phelan stepped down at Mr Hegseth's urging in April.
One of the highest-ranking civilian leaders of the US Army has stepped down after just 18 months on the job.
No reason was given for the departure of US Army Secretary Dan Driscoll, who is a friend of Vice-President JD Vance, but tensions with Defense Secretary Pete Hegseth have been widely reported.
It marks the latest in a series of shake-ups of the military leadership, with the army especially undergoing major upheaval.
"Secretary Driscoll has been highly effective in advancing President [Donald] Trump's agenda to Make America Strong Again at the Department of the Army by providing outstanding leadership during historic military operations, restoring an emphasis on readiness and lethality, assisting with negotiations between Russia and Ukraine, and more," White House spokeswoman Anna Kelly said in a statement.
The US secretary of the army is responsible for justifying army policy, plans and budgets to the secretary of defense, as well as Congress.
A US Army official, who was not authorised to comment publicly and spoke on condition of anonymity, said Mr Driscoll spoke with Mr Trump on the current state of the army and submitted his resignation.
The official did not provide additional details.
The Pentagon referred questions to the army. Mr Driscoll's resignation was reported earlier on Monday by The Wall Street Journal.
According to a recent report by The Washington Post, several US military leaders warned Mr Hegseth against prolonging large-scale operations against Iran, as US military power was stretched thin across the globe.
Dan Driscoll (centre) with Pete Hegseth (left). (Reuters: Kevin Lamarque)
Mr Driscoll's departure follows the ousting of one of his allies from the army as well as the reduction of a drone program he had championed.
