WASHINGTON: President Donald Trump, in the aftermath of his defeat to Joe Biden, has "fired" Defense Secretary Mark Esper, further fuelling the controversy around his refusal to concede defeat in the election.

The move came with a meagre 10 weeks left in President Trump's tumultuous tenure in the White House, highlighting his unstable relationship with the intelligence and security community, especially if they did not effectively serve his own political ambitions.

President Trump and Esper collided repeatedly over pressure from the White House to deploy federal troops to quash civil unrest, especially in the wake of the Black Lives Matter movement, and the President's plan to abruptly withdraw U.S. troops from Afghanistan; putting the national security establishment's plans under jeopardy.

Democrats lambasted the President's decision to relieve the Defense Secretary of his duties, with Nancy Pelosi adding that Esper's firing was "disturbing evidence that President Trump is intent on using his final days in office to sow chaos in our American Democracy and around the world", stating that "again and again, Trump's recklessness endangers our national security".

Trump has named Christopher Miller, head of the National Counterterrorism Center as acting Secretary of Defense, who not only served as a White House counterterrorism advisor, but also as Deputy Assistant Secretary of Defense for "special operations".