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.) is standing by his tough criticisms of President Trump.

"My thoughts were well thought out," Corker told CNN. "Look, I didn't just blurt them out. My comments — my comments, I stand by them — yes."

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The GOP senator said he had repeatedly tried to share his concerns through private communications and meetings, saying the frustration has been "building for some time" before he decided to speak out.

"Look I've been expressing concerns for some time and it's built over time. I've had private dinners, I've had private phone calls, I've tried to intervene on topics that I thought things were going in a different direction and are not going to be good for our country.

"This is not a new thing, it's been building for some time. And it's a pattern that I think we've fought and expressed for some period of time," he told the news outlet.

Corker, who announced in September his plans to retire after his term, gave one of the sharpest public rebukes to the president.

Trump first took aim at Corker on Twitter, claiming he refused to back the Tennessee senator, who the president said was seeking his endorsement for the 2018 midterms.

Trump said Corker had decided to retire after the president said no.

Corker's chief of staff denied the claim, saying the president had actually encouraged the GOP lawmaker to run again and urged him not to retire.

The Tennessee Republican also took to Twitter to blast Trump, calling the White House "an adult day care center" in one tweet.

Corker also told The New York Times in an interview last week that he is not alone in thinking that Trump could lead the country on the path toward "World War III" and that he is treating the presidency like “a reality show.”

He told CNN that he talked to Vice President Mike Pence, Treasury Secretary Steven Mnuchin Steven Terner MnuchinLawmakers fear voter backlash over failure to reach COVID-19 relief deal United Airlines, unions call for six-month extension of government aid House Democrats plan to unveil bill next week to avert shutdown MORE and Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE following the feud.

Corker, the chairman of the Foreign Relations Committee, also said he would vote against the White House tax reform plan if the measure raised the deficit.

"I want to make sure that it's not something that increases deficits, and I also want it to be tax reform," he said.