Markwayne Mullin: Watch US senator challenge union leader to a fight

Republican Senator Markwayne Mullin challenged union leader Sean O'Brien to a fight in the middle of a Senate hearing.

The heated exchange began after Mr Mullin paraphrased a tweet made about him by Mr O'Brien in June: "What a clown, a fraud. Always has been, always will be. Quit the tough guy act in these Senate hearings. You know where to find me. Any place, anytime cowboy."

Mr Mullin then offered to fight Mr O'Brien at the hearing, saying "Sir, this is a time, this is a place, if you want to run your mouth, we can be two consenting adults, we can finish it here," while pointing to the floor separating the two.

Mr Mullin rose from his seat, before Senator Bernie Sanders, chairman of the committee, intervened and told him to sit down.

"It should never come to that," Mr O'Brien later told the Reuters news agency, "We're not 12 years old anymore." He also said he was willing to sit down with Mr Mullin for a coffee or a beer.