Senator Markwayne Mullin challenged a Teamsters leader to an MMA fight in Tulsa.

The challenge comes three months after the two squared off in a Senate hearing.

On Wednesday, Sean O'Brien tweeted:

"Greedy CEO who pretends like he’s self made. In reality, just a clown & fraud. Always has been, always will be. Quit the tough guy act in these senate hearings. You know where to find me. Anyplace, Anytime cowboy."

Senator Markwayne Mullin responded, by using a screenshot of O’Brien’s tweet, not retweeting:

"An attention-seeking union Teamster boss is trying to be punchy after our Senate hearing. Okay, I accept your challenge. MMA fight for charity of our choice. Sept 30th in Tulsa, Oklahoma. I’ll give you 3 days to accept."

O’Brien has not yet responded to the challenge.