Washington DC - The International Brotherhood of Teamsters' General President Sean O'Brien praised Senator Markwayne Mullin after he was announced as Donald Trump's new pick to lead the Department of Homeland Security.

"If anyone is willing to stand their butt up to protect America, it’s Markwayne Mullin," O'Brien told The Hill after Trump announced he had nominated Mullin to replace Kristi Noem as Homeland Security secretary.

The comment was a reference to a dust-up he and Mullin had during a Senate labor committee hearing back in 2023, in which the Oklahoma Republican challenged the union leader to a fistfight.

In the tense exchange, Mullin said to O'Brien, "You want to run your mouth? We can be two consenting adults. We can finish it here."

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"Okay, that's fine, perfect. I'd love to do it right now," O'Brien responded.

"Then stand your butt up then," Mullin, a former MMA fighter, answered, to which O'Brien replied, "You stand your butt up."

The senator then got to his feet and appeared ready to advance toward the Teamsters president before Senator Bernie Sanders intervened.

Since the viral exchange, the two have apparently gone on to reconcile.

"[O'Brien] said, 'Out of all of the people that I should have read their bio on I should read yours and I didn't,'" Mullin told reporters at the 2024 Republican National Convention.

"And I found it humorous and we sat down and we had a great two-hour conversation. Since then, him and I have talked very often."

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O'Brien referenced his exchange with Mullin during his RNC convention speech, saying both Democrats and Republicans need to "stand their butts up" to deliver for working Americans, while praising Trump as "one tough SOB."

The Teamsters leader faced widespread criticism for becoming the first president in the union's 121-year history to speak at the RNC.

Just one day after his RNC appearance, O'Brien appeared to endorse an op-ed penned by Republican Senator Josh Hawley of Missouri, entitled The Promise of Pro-Labor Conservatism.

Hawley's article claims that corporate efforts to "push diversity, equity, and inclusion and the religion of the trans flag" are hurting American workers. O'Brien shared the article on X, saying the senator was "100% on point."

Under O'Brien's leadership, the union declined to endorse a 2024 presidential candidate for the first time in decades.