A riled-up Donald Trump let loose on everything from the Russia probe, to “crimes” by his opponents, to his legal tangles with a porn star Thursday, in a free-wheeling interview live on TV.

Trump called in to the popular breakfast show “Fox and Friends,” to mark the occasion of First Lady Melania Trump's birthday, he said.

Despite a cosy welcome from the three hosts — regular cheerleaders for the Republican president — the interview almost immediately took an awkward turn when Trump was asked about his gift for his wife.

“Maybe I didn't get her so much,” said the multimillionaire, suggesting he got a card and some flowers. “You know I'm very busy to be running out looking for presents,” he added.

Over the animated half hour that followed, Trump rattled through grievances and boasts in a virtual monologue, delivered at machine gun speed.

He attacked former FBI director James Comey as “guilty of crimes” and vowed retribution for those who helped scuttle his doctor's bid to be head of the Department of Veterans' Affairs.

Amid the scattershot remarks, he also bragged again about his 17-month-old electoral college win — ever aggrieved at losing the popular vote to Hillary Clinton and suggested he had three or four dates in mind to meet North Korean leader Kim Jong Un.

Between favourable questions about why Trump's political opponents oppose him, hosts Steve Doocy, Ainsley Earhardt and Brian Kilmeade appeared shocked and uneasy at some of the president's responses.

At one point, as Trump was mid diatribe about “fake news” CNN, Kilmeade interjected, “yeah, but don't worry about them.” The TV host's efforts were largely in vain.

'Everyone knows it's a fix, okay?'

Time and again the 45th president's thoughts trailed back to his own legal woes, including the Russia investigation that has imperilled his closest aides and threatens to hamstring his entire administration.

“I would give myself an 'A+,'” the US president said. “Nobody has done what I have been able to do, and I did it despite the fact that I have a phony cloud over my head that doesn't exist.”

“Everyone knows it's a fix, okay? It's a witch hunt and they know that and I've been able to message it,” Trump railed.

Trump was at special pains to distance himself from his long-time lawyer, Michael Cohen, who is now under criminal investigation.

“Michael is in business, he is really a businessman, at fairly big businesses, I understand,” Trump said.

“I don't know his business, but it doesn't have to do with me,” he added, sweeping aside their decades-old relationship.

But Trump did make the notable admission that his lawyer-cum-fixer had represented him “with this crazy Stormy Daniels deal.” Trump and the White House have long denied that the president knew anything about Cohen's $130,000 payment to the porn star.

Daniels says the payment, which Cohen admits making, was made to cover up a fling with Trump.

Trump denies having sex with Daniels while married and, more broadly, said he had made a decision to “try to stay away from” the workings of the Justice Department “but pretty soon I won't.”

US media described the appearance as a “rant” and “meandering” but it won over at least one supporter.

“Listening to @realDonaldTrump having fun and swinging from the hips on @foxandfriends and wondering why he hasn't been doing this more. This works.

"He's the best promoter of his own record and people,” said conservative commentator Hugh Hewitt.