Paul Ryan on Tuesday expanded on his remark that Donald Trump's attack on a federal judge was the "textbook definition" of racist, saying in a radio interview that he didn't believe that Trump was racist "in his heart."

In an interview on Fox News Radio's Kilmeade and Friends, the speaker of the House said that he didn't mean to say that Trump was a racist.

"I'm saying that comment was," Ryan said. "I don't know what's in his heart. I can't speak to that whatsoever. What I'm saying is to suggest that a person's race disqualifies them to do their job is textbook. That's what I'm saying. I'm not saying what's in his heart because I don't know what's in his heart and I don't think he feels that in his heart. But I don't think it is wise or justifiable to suggest that a person should be disqualified from their job because of their ethnicity."

Asked by host Brian Kilmeade if he would have re-thought his endorsement of Trump last week had the presumptive Republican nominee made the comments earlier, Ryan said there was no point in re-visiting the decision.

"Well, I won't get into — there's no point of looking back into the past," Ryan said. "Hindsight's a 20/20 thing. I do believe that if the alternative is Donald Trump and Hillary Clinton, I know for certain that Hillary Clinton is not going to work with us on this agenda. I know for certain that Hillary Clinton is promising four more years like the Obama years and that is the wrong path for this country. And I do know for certain, from my lengthy conversations with Donald Trump that this agenda, these ideas, these principles have such a better chance of making into law — I do know that he is going to work with us to take these principles and these policies and make them law. And I know for certain that Hillary Clinton will not do that."