Alan Mendoza, director of transatlantic foreign policy and security think-tank The Henry Jackson Society, agrees that Biden presents a serious risk to the West.

He told The Sun the 81-year-old President failed to quell doubts about his mental capacity at the summit and is an embarrassment.

Alan said: "It is embarrassing, I think, because these kind of gaffes, public, in front of the world's eyes, are not what you'd expect a president to be doing."

This week's slip-up from Biden was the latest in a string of blunders the President has been ridiculed for as even his most senior Democratic colleagues call for him to quit.

Even former President Barack Obama is thought to be manoeuvring behind the scenes to get him out of the race.

Reports also surfaced last week of an anonymous document titled “Unburdened by What Has Been: The Case for Kamala”.

Shared amongst democrats, it lays out a detailed plan for replacing Biden with Vice President Kamala Harris.

JOE NEEDS TO GO NOW

Richard told The Sun Biden's performance this week would have been "very, deeply concerning for many members of Nato".

He said: “To mistake Zelensky for Putin is about the worst thing he could do.

"It's very, very, offensive, obviously, unintentionally offensive, but nevertheless... The President of the United States cannot afford to give unintentional insults of that sort."

Joe Biden calls Trump his VP in mix-up with Kamala Harris – seconds before hitting back at questions about Putin gaffe

Richard warned The Sun that Biden's mental fitness gives "pleasure and encouragement" to vicious foreign actors like Russia and China.

He said it gives dictators Xi Jinping and Putin a less than intimidating picture of the "state of the person that's supposed to be leading our defensive alliance".

Richard told The Sun: "I think he appears to be unwilling to stand down himself. The Democratic Party and the US government needs to make sure he's not the next president.”

“He should be ruled out of the president's race on mental health grounds."

It's not enough just to say he shouldn't stand for election, he should be replaced now by the Vice President. He needs to be taken out of office now
Richard Kemp

The ex-colonel, who served across the globe in multiple wars since 1977, said the world is at a "very, very critical period" of "worsening security".

“It's not enough just to say he shouldn't stand for election, he should be replaced now by the Vice President. He needs to be taken out of office now," Richard said.

“And the vice president has a duty to... replace him as President, and that should happen immediately.

"A lot could happen in the next six months. That's very dangerous if he remains at the helm."

Richard added: "And it's not just to the United States, obviously, it's very, very important to the whole of the free world, including the United Kingdom."

Biden had a disastrous debate with former President Donald Trump a few weeks ago

Former President Barack Obama - a long-time friend of Biden - reportedly feels he should pull out too

THREAT TO GLOBAL SECURITY

Alan told The Sun of this week's Nato summit: "He [Biden] ruined it by those two big whoppers," referring to his mistakes about Kamala Harris and Zelensky.

He added: "It's very difficult to see how you would get Zelensky and Putin confused.

"The Kamala Harris one was in a sense, worse because he didn't recover from it. He just went on as if it hadn't happened, saying that she was Vice President Trump instead.

"It is embarrassing, I think, because these kind of gaffes, public, in front of the world's eyes, are not what you'd expect a president to be doing."

It is embarrassing, I think, because these kind of gaffes, public, in front of the world's eyes, are not what you'd expect a president to be doing
Alan Mendoza

Biden's apparent "confusion", Alan said, is dangerous, as it weakens the entire military alliance and wider west in the eyes of actors like Russia, China or Iran.

He said: "It's quite clear that his performance is deteriorating over time. In the last six months to a year, it's been much worse.

"If you're Putin, Xi or Khamenei, you're looking at this and going 'Is this man really gonna stop us from doing what we want to do?'," Alan explained.

"And that's a challenge for global security. You need to have an American president who is perceived to be stronger.

"If you don't have the perception, you encourage bad actors to believe that they will be able to get away with bad activity purely on account of confusion from their opponent."

Alan thinks the the Biden predicament facing the Democratic party is "obvious", as he needs to resign.

He told The Sun it would be the "cleanest" scenario for Biden to step down now as President and allow Kamala to replace him immediately.

But failing that, a "neat solution" would be for Biden to be removed under the 25th Amendment - also likely replacing him with Kamala.

Alan said of Biden resigning: "Well, that, of course, would be the cleanest solution, because that would enable Kamala Harris to step in as president.

He went on: "If he did step down, though, or was frankly removed under Amendment 25 of the constitution, which says that if you're incapable... That would be neat as a solution."

But Alan added: "I don't think he's at that stage where you could probably make that judgement and say he's obviously totally incapable.

"So I think it really is down to whether he decides to resign and hand over or not."

While Alan said is it up to the Democratic Party to decide whether it is time for Biden to go, he described the President as a "liability" and said he would advise him to pull out.

Alan told The Sun: "He claims that other world leaders came up to him and said, oh, we hope you win against Trump," after the DC summit.

"That's not great to reveal what people are telling you in private conversations," Alan explained.

"Clearly, he's turning into a bit of a liability, not simply at home, but also abroad, if he's sharing these kinds of conversations in public."

But the analyst doesn't believe Biden is likely to resign.

He told us: "The Joe Biden we've seen is very solid, very convinced that he is still fit for office, very hurt by the idea he isn't.

"If I was the Democratic Party, I would be going, 'polls show us that almost all the other candidates we have will beat Donald Trump handsomely.