U.S. Army Secretary Dan Driscoll has played a role in Washington's efforts to end Russia's war against Ukraine and previously advocated for closer U.S.-Ukraine military cooperation.

Army Secretary Dan Driscoll submitted his resignation to President Donald Trump, three sources familiar with the matter told CNN.

Dan Driscoll had been rumored to step down at some point between now and the end of the year but the White House announced his departure Monday.

The development follows Driscoll publicly breaking with Hegseth's move to force Gen. Randy George, the ousted Army chief of staff, to retire.