Dozens of top Republican security officials back Joe Biden and slam Donald Trump with one saying: 'He's a despicable human being and the worst president in American history - it's not even close.'

After the Democratic Convention ends Thursday night with Joe Biden officially accepting his nomination, more than 70 former Republican national security officials plan to endorse the Democratic candidate and condemn President Donald Trump.

'Trump has demonstrated that he lacks the character and competence to lead this nation and has engaged in corrupt behavior that renders him unfit to serve as president,' the 73-strong group plans to declare in a full-page ad in The Wall Street Journal on Friday.

'We have concluded that Donald Trump has failed our country and that Vice President Joe Biden should be elected the next President of the United States,' the copy adds.

The group, called Former Republican National Security Officials for Biden, includes many considered the most senior Republicans members of the U.S. defense and intelligence establishment and they have served in administrations spanning from Ronald Reagan, George H.W. Bush, George W. Bush and even under Trump himself.

Bob Tuttle, who served as director of personnel under Reagan and ambassador to the UK under Bush Jr., is a member of the national security group called Trump's handling of the coronavirus crisis had been 'abominable.'

'He's a malignant narcissist. He's a liar. He's a despicable human being and the worst president in American history - it's not even close,' he told Reuters.

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A group of 73 former Republican national security officials will endorse Joe Biden on Friday and condemn Donald Trump as a 'liar,' 'abominable' person and a 'narcissist'

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The group includes John Negroponte (left), the first director of National Intelligence and William Webster (right), the only man to serve as both head of the CIA and FBI

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General Michael Hayden, who served as national security director and head of the CIA under George W. Bush, is also part of the Republican group

Another group member, James Glassman, an undersecretary of state in the George W. Bush administration, said Trump had created 'global chaos.'

'Lack of leadership has led to the deaths of 170,000 Americans,' Glassman said. 'There's no excuse in the country with the best health scientists in the world.'

Their full-throated condemnation of Trump and backing of Biden will come three days before the Republican nominating convention opens on Monday.

It will attempt to ipstage the four-day event by underscoring how the president has alienated some members of his own party, especially among intelligence and foreign policy veterans.

The group also includes the likes of retired General Michael Hayden, who served as national security director and head of the CIA; William Webster, the only man to serve as both head of the CIA and FBI; John Negroponte, the first director of National Intelligence; Michael Leiter, former director of the National Counterterrorism Center; and Mike Donley, former secretary of the Air Force.

The group is one of a number of Republican organizations opposing Trump's re-election in the Nov. 3 election – one of the most notable and vocal being The Lincoln Project, which is headed by Trump's Senior Counselor Kellyanne Conway's husband George Conway.

Collectively, the more than six dozen individuals object to Trump's alienation of U.S. allies abroad and his leadership at home.

Most recently they are critical of his response to the coronavirus pandemic, which has killed more than 170,000 Americans and triggered a severe economic downturn.

The Trump campaign has described Republican-led groups campaigning for Biden, such as Republican Voters Against Trump, as 'the swamp' and disaffected former officials 'trying to take down the duly elected President of the United States.'

One of those groups is 43 Alumni for Biden, which includes hundreds of officials who worked for George W. Bush who oppose Trump's reelection.

Trump himself has expressed contempt, saying on Twitter last year that such 'Never Trump Republicans' are 'human scum.'

The group lays out a detailed charge sheet against Trump, including accusations that he is unfit to lead in a national crisis, undermined confidence in U.S. elections, aligned himself with dictators, preached a 'dark and pessimistic view of America' and attacked and vilified immigrants.

The national security group will launch a website on Friday and come under the umbrella of another anti-Trump organization run by Republicans, Defending Democracy Together. The former national security officials raised $140,000 among themselves to launch their effort.