(CNN) Senate Republicans sharply pushed back on President Donald Trump's reported demeaning comments about Attorney General Jeff Sessions, with one top GOP senator comparing the President's tirades to a "whining" teenager.

"If the President doesn't like his service, he can look him in the eye and terminate him," Senate Foreign Relations Chairman Bob Corker told CNN. "Whining is pretty unbecoming of a 13-year-old. But it's very unbecoming of a 71- or 72-year-old President."

Corker, a retiring Tennessee Republican, added that Trump's disdain for institutions like the Justice Department shows his "lack of appreciation for democratic values and institutions," warning he would turn the country into Venezuela "if left to his own accord."

As a retiring Republican, Corker often is a rare voice criticizing a number of the President's controversial statements and actions. But on Tuesday, more Republicans began to speak out about Trump's comments attacking Sessions, which were reported in the book by journalist Bob Woodward. In the book, the President reportedly called the attorney general, who is from Alabama, a "dumb southerner" and "mentally retarded." Trump has for months lashed out at Sessions because he recused himself from overseeing the Russia probe since the former senator served as a top surrogate for the Trump campaign in 2016.

As senators on Tuesday began to digest the new comments, more began to push back.

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