Dr Bandy X Lee, who was reportedly called upon by concerned members of Congress, believes the US president’s mental health is a mounting emergency.

The Congressmen called on the internationally recognised expert on violence to brief them about the President’s recent behaviour, reported the Daily News.

Dr Lee, who edited the book The Dangerous Case of Donald Trump: 27 Psychiatrists and Mental Health Experts Assess a President, made her case in a closed-door meeting over two days in December.

She told the New York Daily News: “From a medical perspective, when we see someone unraveling like this, it’s an emergency.

“We’ve never come so close in my career to this level of catastrophic violence that could be the end of humankind.”

The 25th amendment to the US Constitution says the vice-president or the majority of the cabinet could write to Congress demanding the President's removal if they were “unable to discharge the powers and duties of office".

This has led to speculation that Trump could be impeached over possible mental health concerns.

Noting that psychiatrists are prohibited from diagnosing from afar, Dr Lee pointed to President Trump’s pattern of behaviour as a worrying sign.

She said Trump was “very attracted to means of violence as a way of burnishing power”.

The response from the lawmakers was “overwhelming”, she added.

Dr Lee held a small conference for mental health professionals last April to discuss their “duty to warn” about a leader’s psychological instability.

Though only about 20 people attended, many lawmakers contacted Dr Lee later and she eventually gained the support of more than 1,000 mental health professionals.

This week, Trump responded to North Korean leader Kim Jong-un’s threat of a missile strike on the US with a “nuclear button on his office desk".

Trump responded on Twitter and wrote: “Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!”

The tweet prompted Richard Painter, a former ethics lawyer under President George W Bush, to declare Trump “psychologically unfit".