The comments come as Trump has escalated his attacks against U.S. District Court Judge Gonzalo Curiel, who last week ordered parts of internal documents, including "playbooks" regarding running the enterprise, to be released as part of a lawsuit against Trump University. The documents were released in response to a request by The Washington Post.

Ryan's criticism -- coming one day after he endorsed his party's presumptive presidential nominee -- came unprompted during an interview on a Wisconsin radio station.

"Look, the comment about the judge, just was out of left field for my mind," Ryan said on WISN in Milwaukee . "It's reasoning I don't relate to, I completely disagree with the thinking behind that."

And then Ryan issued a warning to Trump that he will speak out when he feels he needs to.

"So he clearly says and does things I don't agree with and I've had to speak up on time to time when that has occurred and I'll continue to do that if that's necessary -- I hope it's not," Ryan said.

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A top Republican official said Friday night that Trump's comments on Curiel are making huge waves in the party. "Awful," the official said. "We are all beside ourselves."

The official went on to say, "You have to feel for Paul Ryan," who had just announced his support for Trump before the billionaire told The Wall Street Journal Thursday night that Curiel had a conflict of interest due to his heritage.

A Trump official told CNN, "It's no reason to celebrate, (but) no reason to panic," an indication there is concern inside the campaign but they don't believe it's damaging long-term.

Another campaign adviser laughed when asked if Trump campaign officials can talk to the candidate about watching what he says.

Friday night, Republican Arizona Sen. Jeff Flake condemned Trump's rhetoric on Curiel.

".@realDonaldTrump's comments were ignorant, offensive & suggest a troubling disregard for the separation of powers," Flake tweeted.

.@realDonaldTrump's comments were ignorant, offensive & suggest a troubling disregard for the separation of powers https://t.co/osho3EozfF — Jeff Flake (@JeffFlake) June 3, 2016

Clinton lashes into Trump

Later in the day, Clinton, the likely Democratic nominee, said Trump "has gone so far as to insult and attack a distinguished federal judge, a man who was appointed on his merits, a man born in Indiana, which last time I checked was part of America, to two Mexican parents, who is presiding now, the judge is, over a lawsuit pointing out how fraudulent Trump University is.

Speaking at a campaign event in Westminster, California, Clinton called Trump University "a con game that has benefited Donald Trump but hurt so many people including those who couldn't afford it" and added that the judge is "doing his job, that is what he got appointed to do."

Earlier in the day, Lorella Praeli, director of Latino outreach for the Clinton campaign, praised Curiel's experience and qualifications, saying, "Judge Curiel and his family epitomize the American Dream. His parents worked hard to give their U.S.-born children a better life. He and his brother became successful lawyers. His other brother served in Vietnam."

"In Trump's version of America, this Latino family isn't really America. But they are America. And Hillary Clinton will fight for ALL Americans," Praeli wrote.

Trump has controversially gone after Curiel, who is presiding over a class-action lawsuit against Trump's now-defunct training program in California, and suggested his "Mexican heritage" could prevent him from judging Trump fairly as a result of Trump's strident anti-immigration rhetoric.

Trump on Friday vociferously defended his claims about Curiel and pushed back against criticism.

"He's proud of his heritage. I respect him for that," Trump told CNN's Jake Tapper, dismissing charges that his allegation was racist. "He's a Mexican. We're building a wall between here and Mexico."