Democrats in Congress laid plans on Friday for the swift impeachment of Donald Trump, demanding immediate action to ensure the “unhinged” president cannot add to the damage they say he has inflicted, or even ignite nuclear war in his final days in office.

As the country comes to terms with the violent siege of the US Capitol by Trump supporters that left five dead, the crisis that appears to be among the final acts of his presidency is deepening like few other periods in the nation’s history.

With less than two weeks until he has gone, Democrats want him out — now — and he has few defenders speaking up for him in his own Republican party.

“We must take action,” House Speaker Nancy Pelosi declared on a private conference call with Democrats.

And one prominent Republican, Senator Lisa Murkowski of Alaska, told the Anchorage Daily News that Mr Trump simply “needs to get out”.

The final days of Trump’s presidency are spinning toward a chaotic end as he holes up at the White House, abandoned by many aides, top Republicans and Cabinet members. He also had his favourite means of communication – Twitter – taken away, after the company suspended his account permanently.

After refusing to concede defeat in the November election, he has now promised a smooth transfer of power when Democratic President-elect Joe Biden is sworn in on January 20.

But even so, he says he will not attend the inauguration — the first such presidential snub since just after the Civil War. Mr Biden welcomed this development as “a good thing”, calling the president an “embarrassment” to the nation and unworthy of the office.

In Congress, where many have watched and reeled as the president spent four years breaking norms and testing the nation’s guardrails of democracy, Democrats are unwilling to take further chances with only a few days left in his term.

The mayhem that erupted on Wednesday at the Capitol stunned the world and threatened the traditional peaceful transfer of power.

Ms Pelosi said she had spoken to the chairman of the Joint Chiefs of Staff, General Mark Milley, “to discuss available precautions for preventing an unstable president from initiating military hostilities or accessing the launch codes” for nuclear war.

She said Gen Milley assured her long-standing safeguards were in place.

The president has sole authority to order the launch of a nuclear weapon, but a military commander could refuse the order if it were determined to be illegal. Mr Trump has not publicly made such threats, but officials warn of grave danger if the president is left unchecked.

“This unhinged president could not be more dangerous,” Ms Pelosi said of the current situation.

Mr Biden, meanwhile, said he was focused on his job as he prepares to take office. Asked about impeachment, he said, “That’s a decision for the Congress to make.”

The Democrats are considering lightning-quick action. A draft of their Articles of Impeachment accuses Mr Trump of abuse of power, saying he “willfully made statements that encouraged — and foreseeably resulted in — imminent lawless action at the Capitol”, according to a person familiar with the details who was granted anonymity to discuss them.

The articles are expected to be introduced on Monday, with a House vote as soon as Wednesday.

If Mr Trump were to be impeached by the House and convicted by the Senate, he might also be prevented from running again for the presidency in 2024 or ever holding public office again.

He would be only the president twice impeached. A person on the call said Ms Pelosi also discussed other ways Mr Trump might be forced to resign.

Senators from a bipartisan group convened their own call to consider options for congressional action, although Trump spokesman Judd Deere said: “A politically motivated impeachment against a President with 12 days remaining in his term will only serve to further divide our great country.”

After an initial 12-hour Twitter ban expired, Mr Trump was tweeting again on Friday. But having posted a calm video on Thursday decrying the violence, he reverted to an aggressive statement that his supporters must not be “disrespected”. In the evening, Twitter said it was permanently suspending him from its platform, citing “risk of further incitement of violence”.

The soonest the Senate could begin an impeachment trial under the current calendar would be January 20, Inauguration Day.

Conviction in the Republican Senate at this late date would seem unlikely, though in a sign of Mr Trump’s shattering of the party, many Republicans were silent on the issue.

One Trump ally, Republican Minority Leader Representative Kevin McCarthy of California, did speak up, also saying that impeaching the president at this late stage “will only divide our country more”.

Mr McCarthy said he planned to speak with Mr Biden about working together to “lower the temperature”.

Ms Murkowski said: “I want him out. He has caused enough damage.”

Another leading Republican critic of Mr Trump, Senator Ben Sasse of Nebraska, said he would “definitely consider” impeachment.

Independent senator Bernie Sanders tweeted that some people ask, why impeach a president who has only a few days left in office?

“The answer: Precedent. It must be made clear that no president, now or in the future, can lead an insurrection against the U.S. government,” Mr Sanders said.

Ms Pelosi and Democratic Senate leader Chuck Schumer have called on vice president Mike Pence and the Cabinet to invoke the 25th Amendment to to force Trump from office but that appears unlikely.