Sen. Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (R-Tenn.) said Tuesday that he does not believe President Trump's behavior has improved since he took office in January, saying it instead appears to be "devolving."

"I've seen no evolution in an upward way," Corker told reporters on Capitol Hill. "As a matter of fact, I would say, it appears to me it's almost devolving.

"You would think he would aspire to be the president of the United States and act like a president of the United States. But, you know, that's just not going to be the case apparently."

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The comments were Corker's latest jab at Trump. The two have sparred sporadically in recent weeks, but their war of words rose to new heights on Tuesday, with both men trading escalating criticism hours before Trump was set to attend a lunch with GOP senators on Capitol Hill.

The back-and-forth on Tuesday began with Corker levying criticisms of Trump's foreign policy in an interview on NBC's "Today" show.

Trump later took to Twitter to accuse Corker of trying to upend his legislative agenda. Trump also revived a previous claim that the Tennessee Republican — who announced last month that he would not seek reelection in 2018 — had decided not to run because Trump would not endorse him.

In interviews on Capitol Hill on Tuesday, Corker denied Trump's allegations, saying the president has "great difficulty with the truth."

"Unfortunately I think world leaders are very aware that much of what he says is untrue," Corker told CNN. "I don't know why he lowers himself to such a low standard. It debases our country."