David Letterman unleashed a flood of his opinions on 'crazy' Trump, saying the Russians 'groomed' him and predicted the president 'will eventually take a fastball to the face and have to leave the game'.

Although Letterman has stepped away from his late night television show and insists he wants no part of the late night circuit, he admits he would take one last swing at the president.

The 69-year-old comedian was serious when he declared that he was 'sure the Russians groomed' Trump and predicted that with the help of comedy poking at the president, he will 'have to leave the game.'

Letterman said: 'I’m sure the Russians groomed Trump. They gave him tips: “You want to be an authoritarian dictator? Sure, that’s not a problem. We’ll tell you how to do it, for God’s sake".'

David Letterman unleashed a flood of his opinions on 'crazy' Trump, saying the Russians 'groomed' him and predicted the president 'will eventually take a fastball to the face and have to leave the game'

The former host of the Late Show didn't hold back his thoughts on Trump, someone who he has been interviewing since the 1980s. He said: 'I always regarded him as ... a joke of a wealthy guy. He was big and doughy and you could beat him up'

The retired host unleashed all his thoughts surrounding the president in a wide-ranging interview with New York Magazine's Vulture, published on Sunday.

He continued that comedy was playing a role in helping disarm Trump, making an analogy to a baseball batter trying to concentrate on hitting the ball but continually swatting away flies.

Letterman said: Well, that’s Alec Baldwin and Saturday Night Live. It’s distracting the batter. Eventually Trump’s going to take a fastball off the sternum and have to leave the game.'

He also attacked Jimmy Fallon's infamous hair tussle of the president when he was a candidate, criticized the president's administration and called 'Trumpy' a 'joke of a wealthy guy'.

Letterman thought Fallon's interview with Trump was a wasted opportunity by not asking serious questions, choosing instead to touch his hair to prove it was real for a laugh.

The former Late Show host said: 'I don’t want to criticize Jimmy Fallon, but I can only tell you what I would have done in that situation: I would have gone to work on Trump.'

David Letterman thought Jimmy Fallon's interview with Donald Trump (pictured) was a wasted opportunity when the comedian ruffled the president's hair for a laugh

After stepping away from 33 years as a late night host, Letterman said he didn't regret his retirement and doesn't even feel the urge to watch other late night shows.

It wasn't until Trump came on the scene, someone Letterman has interviewed since the 1980s, that made him reconsider who he would take his last swing at.

He said to Vulture: 'I always regarded him as ... a joke of a wealthy guy. He’d sit down, and I would just start making fun of him. He never had any retort. He was big and doughy and you could beat him up.'

If he was to return for one more hour of late night television, Letterman says he would interview Trump and pointedly said he would call him out on lies.

Although Letterman retired after 33 years on TV, he said he would take one more swing at 'crazy' Donald Trump. The 69-year-old said he thinks comedy is helping to disarm Trump

He added: 'I think I would be in the position to give him a bit of a scolding and he would have to sit there and take it. Yeah, I would like an hour with Donald Trump; an hour and a half.'

However, Letterman said that if he still was on air today, there wouldn't be enough time to fit in all his political comments on Trump and his staff.

He said: 'It’s such an amazing group of targets. The comedy potential of these people is incredible. It’s delightful. Kellyanne Conway was my favorite for a long time.

'And who’s this goon Steve Bannon... the Hunchback of Notre Dame. Bannon looks like a guy who goes to lunch, gets drunk and comes back to the office.

'And poor Sean Spicer is a boob who just got out of a cab and now here he is.

'Stephen Miller. Wow, that guy is creepy. He fell out of a truck.'

Letterman said that if he still was on air today, there wouldn't be enough time to fit in all his political comments on Trump and his staff