Washington(CNN) Former FBI Director James Comey says he's unsure if he believes President Donald Trump's denial that he interacted with prostitutes during a trip to Russia in 2013.
"Honestly, I never thought these words would come out of my mouth, but I don't know whether the current President of the United States was with prostitutes peeing on each other in Moscow in 2013," Comey said in a clip of an interview with ABC News that aired Friday on "Good Morning America." "It's possible, but I don't know."
The allegations that Russian authorities recorded Trump watching prostitutes urinate in a hotel suite were included in a dossier -- portions of which remain unconfirmed -- that was commissioned as opposition research during the 2016 election and compiled by a former British intelligence agent, Christopher Steele.
There is no indication that such a tape exists and Trump has vehemently denied it.
In his book, of which CNN has obtained a copy, Comey writes that Trump spoke to him on four separate occasions to deny the prostitution allegation.
Trump brought up the dossier again at a private dinner with Comey at the White House in January 2017.
"He says he may want me to investigate it to prove that it didn't happen," Comey told ABC News. "And then he says something that distracted me."
Comey went on to recall, "(Trump) said, 'If there's even a 1% chance my wife thinks that's true, that's terrible.' And I remember thinking, 'How could your wife think there's a 1% chance you were with prostitutes peeing on each other in Moscow?'"
Comey told ABC News that he did not inform Trump that the dossier had been financed by Trump's political opponents.
When asked if he thought Trump deserved to know that, Comey said, "I don't know the answer to that."
"It wasn't necessary for my goal, which was to alert him that we had this information," he said.
Trump tore into Comey Friday morning, calling him a "weak and untruthful slime ball" and a "proven LEAKER & LIAR."
The White House and the Republican National Committee have been working to discredit Comey, using Democratic criticism of how Comey handled the investigation into Hillary Clinton's emails, and arguing that he's a leaker trying to sell a self-aggrandizing book.