Overeem was due to challenge Heavyweight champion Junior dos Santos in the main event at UFC 146, but returned a positive sample when representatives of the Nevada State Athletic Commission (NSAC) conducted a random drugs test following a press conference for the event last week.

Six fighters due to fight on the card were tested, and when White discovered that Overeem had returned a positive sample, he launched into a foul-mouthed rant that the former K1 champion had fallen foul of the authorities strict guidelines on performance-enhancing drugs..

He raged: "I am beyond ******* about this. I'm so ******* mad right now I can't even begin. The worst part is that he sat in front of us and lied to us.

"You're an absolute moron, a brain-dead absolute ******* dummy.

"How ******* stupid do you have to be? Seriously dumb. Anybody who's using [performance-enhancing drugs] right now is an absolute ******* moron."

Doubt

The main event is now under threat and Overeem must apply to the NSAC committee to have his 'B' sample tested, if he wants to be cleared to compete at UFC 146.

White admitted that there was no contingency plan in place, and is unsure of how the organisation will proceed if the 31-year-old is banned.

One possibility is promoting either Frank Mir or Heavyweight champion Cain Velasquez to the main event as they face each other on the same card, but White insists he has not decided how he will proceed yet.

He conceded: "There is no Plan B."