Sen. John Thune, R-S.D., said that he is not "afraid of a fight" if former President Donald Trump campaigns against him in 2022 after being labeled a "weak and inneffective RINO" by him earlier in the year.

"I've been through wars in South Dakota, political wars, with my own party when I ran the first time, with the Democrats in a couple of hotly contested Senate races, so being afraid of a fight or somebody coming after me is not something that's going to influence that decision," Thune told "Fox News Sunday."

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Thune has yet to officially announced that he's running for re-election, but said he will provide an update on this in due time.

"I will announce something on my re-election plan, as I typically do, later in the year," he said on Sunday. "I think these campaigns are way too long, cost way too much, and I think the American people -- I know people in South Dakota -- get weary of it, so I'm going to focus on doing the job, which I think is the best way to run for re-election in any election cycle. Who gets in against me is not going to be a factor in that decision."

U.S. President Donald Trump participates in a meeting on trade with governors and members of Congress at the White House on April 12, 2018 in Washington, DC. Seated left is Sen. John Thune (R-SD). (Photo by Chris Kleponis - Pool/Getty Images) ((Photo by Chris Kleponis - Pool/Getty Images))

As Senate Minority Whip, Thune is Senate Minority Leader Mitch McConnell's second-in-command. Trump, who's been critical of Thune and other members of Republican leadership, blasted McConnell as a "dumb son of a b----" at a gathering of Republian donors at Mar-a-Lago on Saturday night.

"I think a lot of that rhetoric is, you know, it's part of the style and tone that comes with the former president, but I think he and Mitch McConnell have a common goal, and that is getting the majority back in 2022," Thune said. "Hopefully that'll be the thing that unites us because if we want to defeat and succeed against the Democrats and get that majority back, that's the best way to do it."

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Trump previously called for South Dakota Gov. Kristi Noem to challenge Thune in 2022, calling Thune a "RINO," or "Republican In Name Only." Thune drew Trump’s ire recently after he criticized Trump’s bid to challenge the results of the 2020 presidential election.

Trump also referred to Thune as "Mitch’s boy," in a reference to McConnell, and warned that Thune would be "primaried in 2022, political career over."

Fox News' Brie Stimson and Fox Business' Thomas Barrabi contributed to this report.