Trump told NBC News that he was frustrated by the ongoing investigation and believed it was motivated by Democrats' fury at losing the election.
It was the first time that Trump had explicitly tied the Russia probe to his rationale for firing Comey. It was one of a series of explanations for dismissing the FBI director, some of which directly contradict those offered earlier by top White House officials.
Trump told NBC's Lester Holt: "And in fact when I decided to just do it, I said to myself, I said 'you know, this Russia thing with Trump and Russia is a made-up story, it's an excuse by the Democrats for having lost an election that they should have won'."
The interview on Thursday capped a week of contradictory statements on Comey.
• On Tuesday, the White House said Trump had fired Comey solely on the recommendation of the deputy attorney general
, who sharply criticized the handling of the investigation into Hillary Clinton's use of a private email server as secretary of state.
• That explanation was repeated multiple times
on Wednesday by Vice President Mike Pence, senior adviser Kellyanne Conway and other White House officials. "He provided strong leadership ... to act on the recommendation of the deputy attorney general," Pence told reporters on Capitol Hill.
• But late on Wednesday -- after earlier meeting Russian Foreign Minister Sergey Lavrov and US ambassador Sergey Kislyak -- Trump said he had fired Comey "because he wasn't doing a good job
• In his NBC interview on Thursday, Trump further contradicted his officials, saying he would have dismissed Comey whatever the deputy attorney general had said, describing him as a "showboat" who had lost confidence of many in the bureau.
• Trump also admitted that Comey's removal could lengthen the Russia investigation. Earlier, White House spokeswoman Sarah Huckabee Sanders
said the FBI director's dismissal would allow the probe to "come to its conclusion with integrity."
• Separately, the acting FBI director Andrew McCabe denied Trump's suggestion that Comey had lost the support of rank-and-file employees at the bureau. McCabe told a Senate hearing
Thursday that Comey enjoyed "broad support" at the FBI.
• Friday morning, Trump defended his surrogates
and their shifting statements.
"As a very active President with lots of things happening, it is not possible for my surrogates to stand at podium with perfect accuracy!....," he tweeted.
Russia probe needs to be 'done properly'
In his NBC interview, Trump denied that he wanted to derail the FBI's Russia investigation. The probe, Trump said, needs "to be absolutely done properly."
"I want that to be so strong and so good," he said. "I want to get to the bottom. If Russia hacked, if Russia did anything having to do with our election, I want to know about it." The President has long insisted the investigation will not discover any wrongdoing. He also reiterated his longstanding claim that he "has nothing to do with Russia," saying he doesn't own property there and has had no business ties aside from hosting the Miss Universe pageant in Moscow "a long time ago."
But Trump's admission that the Russia investigation was on his mind when he fired Comey prompted suggestions that he could be accused of obstructing justice.