Reuters Staff–

Former FBI Director James Comey said he cautioned President Donald Trump against ordering an investigation into salacious allegations in an intelligence dossier about a Trump trip to Moscow in 2013, according to an ABC interview broadcast on Friday.

“I said to him, ‘Sir that’s up to you but you want to be careful about that because it might create a narrative that we’re investigating you personally and, second, it’s very difficult to prove something didn’t happen,” Comey said.

In the first excerpt of an interview with the fired Federal Bureau of Investigation director, broadcast on “Good Morning America,” Comey talked about his initial encounters with the new president, whom he described as volatile, defensive and concerned more about how his own image than about Russian meddling in the 2016 election.

Comey, who was fired by Trump in May, is doing a series of media interviews that coincide with the release next week of his book, “A Higher Loyalty: Truth, Lies and Leadership.”

Trump, who has criticized Comey repeatedly before and after he fired him, denounced him on Twitter on Friday: “James Comey is a proven LEAKER & LIAR,” he said.

In the book, Comey wrote that Trump raised the dossier with him at least four times during meetings, according to the Washington Post, which obtained a copy. The dossier was compiled by former British intelligence officer Christopher Steele about Trump’s ties to Russia and included an allegation that involved prostitutes.

Comey told ABC that Trump denied the allegations and said he may want the FBI to investigate allegations in the dossier to prove they were not true.

Trump was worried there was a chance his wife, Melania Trump, would believe the allegations.

Reporting by Doina Chiacu; Editing by Steve Orlofsky