US Speaker of the House Nancy Pelosi said on Friday she had talked to top military officials about preventing an "unhinged" President Donald Trump from ordering a nuclear strike.
"This morning, I spoke to the Chairman of the Joint Chiefs of Staff Mark Milley to discuss available precautions for preventing an unstable president from initiating military hostilities or accessing the launch codes and ordering a nuclear strike," Pelosi wrote in a letter to House Democrats.
"The situation of this unhinged President could not be more dangerous, and we must do everything that we can to protect the American people from his unbalanced assault on our country and our democracy," she added.
This came two days after a violent riot stormed through the Capitol building as lawmakers from the House and Senate were gathered to confirm Electoral College votes and Joe Biden's victory in the November 3 presidential election.
Five people died in the mob including a police officer, a woman shot by police, and three people who suffered medical emergencies on site.
Pelosi and her counterpart in the Senate, Chuck Schumer, on Thursday called on Vice President Mike Pence to invoke the 25th Amendment which allows for a majority of Cabinet to remove the President from office.
They argued that "the President's dangerous and seditious acts necessitate his immediate removal from office" but Pence has yet to respond.
The Democrats are now mulling impeachment proceedings against the president for a second time.
But Kevin McCarthy, the Republican leader in the house, said in a statement that "impeaching the President with just 12 days left will only divide our country more."
"I have reached out to President-elect Biden today and plan to speak to him about how we must work together to lower the temperature and unite the country to solve America's challenges," he wrote.
Biden, 78, is to be inaugurated on January 20. Trump tweeted on Friday that he will not be attending the inauguration, undercutting an earlier statement that he would ensure a "smooth, orderly and seamless transition of power" to his successor.
He has not yet divulged what he would do on the day.
In a video released on Thursday, Trump said that "serving as your president has been the honour of my lifetime". He also hinted that he may seek to return to the public arena, telling his supporters "our incredible journey is only just beginning."