Former FBI Director James Comey testifies before the Senate Intelligence Committee on Capitol Hill June 8, 2017 in Washington, DC.

President Donald Trump went on a Twitter rampage Sunday morning, blasting former FBI Director James Comey on Twitter as "slippery" and predicting Comey will be remembered "as the WORST FBI Director in history, by far!"

Trump's latest rant against Comey came in advance of the former top law enforcement officer's much-anticipated interview with ABC News on Sunday night to promote his new book "A Higher Loyalty: Truth, Lies, and Leadership." The memoir is due out Tuesday.

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Trump unleashed a series of angry tweets at Comey, who has said he believes Trump was effectively demanding personal loyalty before he fired the FBI director last May.

Comey's firing set in motion the appointment of special counsel Robert Mueller, who is investigating possible collusion by Trump's presidential campaign with Russians.

Trump has denied any such collusion and reportedly has considered firing Mueller, as well as Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein out of anger over the probe. Sessions' recusal from the Russia investigation led to Rosenstein appointing Mueller.

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On Friday, before Trump authorized raids on Syria, the president had first referred to Comey as a "slime ball" on Twitter.

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Comey's interview with George Stephanopoulos is being shown on a special edition of ABC's "20/20" at 10 p.m. ET Sunday.

Comey told ABC News that he publicly discussed in 2016 the FBI's investigation into Hillary Clinton's email server because he believed at that time that she would win the upcoming election, and he wanted to prevent her presidency from being seen as "illegitimate."

Comey said he was "operating in a world where Hillary Clinton was going to beat Donald Trump, and so I'm sure that it was a factor."

"I don't remember spelling it out, but it had to have been, that she's going to be elected president and if I hide this from the American people, she'll be illegitimate the moment she's elected, the moment this comes out," according to ABC 's transcript.

CNN reported Friday that the publisher of Comey's book is printing 850,000 copies because of expected high demand.