He was echoing previous concerns by his lawyer, Rudy Giuliani, who said Mr Trump could be “trapped into perjury”.
“So if I say something and he (Comey) says something, and it’s my word against his, and he’s best friends with Mueller, so Mueller might say: ‘Well, I believe Comey,’ and even if I’m telling the truth, that makes me a liar. That’s no good,” President Trump said.
Mr Trump also asserted that he could, if he wanted to, intervene in the investigation, but added that he had chosen not to do so for now.
“I’ve decided to stay out. Now I don’t have to stay out. I can go in, and I could do whatever – I could run it if I want. But I decided to stay out,” he said.
“I’m totally allowed to be involved if I wanted to be. So far, I haven’t chosen to be involved. I’ll stay out.”
In an interview with NBC on Sunday, Mr Giuliani was asked whether the Trump team was stalling about a possible testimony at the Mueller inquiry.
Mr Giuliani said: “I’m not going to be rushed into having him testify so he can be trapped into perjury.”
He added: “When you tell me that he should testify because he’s going to tell the truth and he shouldn’t worry, well that’s so silly because it’s somebody’s version of the truth. Not the truth.”
Mr Giuliani responded by saying: “Truth isn’t truth.” That comment was widely mocked on social media.
Special counsel Mueller is investigating whether President Trump’s campaign team colluded with Russia to influence the outcome of the presidential election.
In 2016, US intelligence agencies concluded that Russia had used a state-authorised campaign of cyber attacks and fake news stories planted on social media in an attempt to turn the election against Mrs Clinton.
Thirty-two people have now been indicted, including four members of Mr Trump’s campaign team and 25 Russians.
The president’s former campaign manager, Paul Manafort, is the first person to go on trial as a result of Mr Mueller’s investigation. However, the charges are not related to the US election but instead to tax evasion and money-laundering stemming from his political consultancy work in Ukraine.