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The Republican senator who challenged a union leader to a fight in the middle of a hearing has defended the threat as a representation of "Oklahoma values".

Senator Markwayne Mullin, a former local MMA fighter, nearly came to blows with Teamsters president Sean O'Brien on Tuesday afternoon.

"If I didn't do that, people in Oklahoma would be pretty upset at me," Mr Mullin later told Fox News.

Elsewhere, he said he would "bite" in a fight.

"I'll do anything, I'm not above it. And I don't care where I bite by the way," he said on the Undaunted Podcast on Tuesday evening.

Hours earlier, Senator Mullin had sat with other members of the Senate Committee on Health, Education, Labor and Pensions to hear testimony from Mr O'Brien, president of the International Brotherhood of Teamsters, one of the country's biggest unions.

When given a chance to question Mr O'Brien, Mr Mullin brought up a social media post on X, formerly Twitter, in which Mr O'Brien called the senator a "greedy CEO who pretends like he's self made" and said he should "quit the tough guy act in these senate hearings".

"You want to run your mouth, we can be two consenting adults, we can finish it here," Mr Mullin said from the dais.

"That's fine, perfect," Mr O'Brien replied.

Mr Mullin rose as if to fight, motioning to take his wedding ring off, before he was scolded by Senator Bernie Sanders.

"Sit down! You're a United State senator, sit down," shouted Mr Mr Sanders, chair of the committee.

The incident rattled the normally sedate Capitol Hill, already abuzz with reports that former House Speaker Kevin McCarthy had been accused of elbowing a fellow Republican in the back.

But Mr Mullin seemed unfazed.

"You're not going to run your mouth at me and expect me to sit there," he told Fox News' Sean Hannity. "And you should have seen the fear in his eyes when I stood up. I'm not joking."

He told CNN on Wednesday that he had been "standing up to the bully."

Appearing on CNN, Mr O'Brien seemed similarly unbowed, calling Mr Mullin "one of 100 of the most powerful people in the country", who was "acting like a 12-year-old in a schoolyard because [he] didn't get [his] way".

Tuesday's run-in was not the first time Mr Mullin and Mr O'Brien faced off.

Earlier this year, Mr Mullin told the union leader to "shut your mouth" during a tense hearing exchange.

Then in June Mr O'Brien posted a photo of Mr Mullin on social media and wrote: "You know where to find me. Anyplace, Anytime cowboy."

Mr Mullin replied: "MMA fight for charity of our choice. Sept 30 in Tulsa, Oklahoma. I'll give you 3 days to accept."

MMA stands for "Mixed Martial Arts". Mr O'Brien appears to have not accepted.