In a lengthy statement, Trump tried to explain his comments about

federal Judge Gonzalo Curiel

, who is overseeing a lawsuit on Trump University. Trump, who had accused the Indiana-born Curiel of bias because of his Mexican heritage, said in his statement that he does not believe "one's heritage makes them incapable of being impartial."

"Based on the rulings that I have received in the Trump University civil case, I feel justified in questioning whether I am receiving a fair trial," Trump said.

He added that he also has "concerns as to my ability to receive a fair trial" due to his status as the Republican Party's nominee and his campaign's focus on illegal immigration.

"Normally, legal issues in a civil case would be heard in a neutral environment. However, given my unique circumstances as nominee of the Republican Party and the core issues of my campaign that focus on illegal immigration, jobs and unfair trade, I have concerns as to my ability to receive a fair trial," Trump said, adding that he does "not intend to comment on this matter any further."

Trump showed signs already in an interview Monday night with Fox News' Bill O'Reilly that he was softening his position on the judge as he seemed to downplay his past criticism of Curiel.

"I don't care if the judge is Mexican or not," Trump told O'Reilly. "All I want him to do is give me a fair shake."

Trump last week repeatedly took aim at Curiel, calling him a "hater" and "a Mexican."

It was a barrage that both Republicans and Democrats widely condemned as inappropriate, inexcusable and some even characterized the remarks as racist.

House Speaker Paul Ryan on Tuesday offered a particularly harsh condemnation of Trump's words, calling them "sort of like the textbook definition of a racist comment."

"I think that should be absolutely disavowed. It's absolutely unacceptable," Ryan said Tuesday morning.

Republican Sen. Mark Kirk said Tuesday that his party's presumptive presidential nominee "does not have the temperament" to hold the job of president, saying he "cannot and will not support" Donald Trump.

"Given my military experience, Donald Trump does not have the temperament to command our military or our nuclear arsenal," he tweeted.

It was sharp criticism from an incumbent who had previously insisted he would support the GOP nominee.

Trump's statement Tuesday also came after the presumptive GOP nominee spoke with his party's chairman Reince Priebus, a Republican source told CNN.

Even former House Speaker Newt Gingrich, who had been floated as a potential running mate for Trump, called Trump's comments about the judge "inexcusable" and "one of the worst mistakes Trump has made."