President Donald Trump grew visibly angry and walked away from an interview with CBS News reporter John Dickerson after Dickerson pressed him for proof that former President Barack Obama had illegally wiretapped Trump Tower.

The wiretapping claims came up when Dickerson asked Trump about his relationship with former President Barack Obama, whom he had accused of conducting unlawful surveillance of him during the 2016 presidential campaign.

"He was very nice to me, but after that, we’ve had some difficulties," said Trump. "So it doesn’t matter. You know, words are less important to me than deeds, and you saw what happened with surveillance."

Dickerson then asked Trump for evidence that Obama had illegally wiretapped him, but Trump wouldn't offer any -- while insisting that "our side has been proven very strongly."

Dickerson contradicted Trump, however, and pointed out that nothing had been proven.

"I just wanted to find out," Dickerson said. "You’re the president of the United States. You said [Obama] was sick and bad."

After some more attempts at getting Trump to present evidence, Trump simply said, "That's enough, thank you," and walked away from the interview.

Watch the whole interview below.