Trump fired off a series of angry tweets on Sunday denouncing a New York Times story that said his White House counsel Don McGahn had cooperated extensively with special counsel Robert Mueller and his team investigating Russian election meddling and potential collusion with Trump's campaign.

"The failing (at)nytimes wrote a Fake piece today implying that because White House Councel Don McGahn was giving hours of testimony to the Special Councel, he must be a John Dean type 'RAT,"' Trump wrote, misspelling the word "counsel," as he often does. "But I allowed him and all others to testify - I didn't have to. I have nothing to hide......"

The New York Times is standing by its story.

Dean, a frequent critic of the president, was the White House counsel for Nixon during the Watergate scandal. He ultimately cooperated with prosecutors and helped bring down the Nixon presidency in 1974, though he served a prison term for obstruction of justice.

Dean tweeted on Saturday night in response to the Times story: "Trump, a total incompetent, is bungling and botching his handling of Russiagate. Fate is never kind to bunglers and/or botchers! Unlike Nixon, however, Trump won't leave willingly or graciously."

He added on Sunday in response to Trump's tweets that he doubts the president has "ANY IDEA what McGahn has told Mueller. Also, Nixon knew I was meeting with prosecutors, b/c I told him. However, he didn't think I would tell them the truth!"

Trump's original legal team had encouraged McGahn and other White House officials to cooperate with special counsel Robert Mueller, and McGahn spent hours in interviews.

Trump's personal lawyer, Rudy Giuliani, said in an appearance on NBC's "Meet the Press" that Trump didn't raise executive privilege or lawyer-client privilege during those interviews because his team believed - he says now, wrongly - that full participation would be the fastest way to close the investigation.

"The president encouraged him to testify, is happy that he did, is quite secure that there is nothing in the testimony that will hurt the president," Giuliani said.

McGahn's lawyer William Burck added in a statement: "President Trump, through counsel, declined to assert any privilege over Mr. McGahn's testimony, so Mr. McGahn answered the Special Counsel team's questions fulsomely and honestly, as any person interviewed by federal investigators must."

Trump on Sunday continued to rail against the Mueller investigation.

"So many lives have been ruined over nothing - McCarthyism at its WORST!" Trump tweeted, referencing the indiscriminate and damaging allegations made by Sen. Joseph McCarthy in the 1950s to expose communists.

"Study the late Joseph McCarthy, because we are now in period with Mueller and his gang that make Joseph McCarthy look like a baby! Rigged Witch Hunt!" he later wrote.

Giuliani, in his interview, also acknowledged that the reason for the June 2016 Trump Tower meeting between Trump campaign aides and a Russian lawyer, arranged by Trump's son Donald Trump Jr., was that they had been promised dirt on Trump's 2016 Democratic rival, Hillary Clinton.

"The meeting was originally for the purpose of getting information about Clinton," he said, adding that the Trump team didn't know that Natalia Veselnitskaya was Russian - even though emails later released by Trump Jr. show that she had been described as a "Russian government attorney."

Australian Associated Press