The hugely-anticipated fight between Conor McGregor and Floyd Mayweather was delayed on Saturday night after online streams of the broadcast crashed due to overwhelming demand.

Thousands of boxing fans were left fuming after the UFC TV stream went down, preventing fans from watching most of the undercard.

Viewers had paid as much as $100 to watch the live stream of the contest in Las Vegas, which is expected to be the biggest pay-per-view event in history.

But the UFC.TV server appeared to crash less than two hours before the main event, just as viewers were preparing to watch the title bout on the undercard between Welshman Nathan Cleverly and Badou Jack.

"Due to high demand, we have reports of scattered outages from various cable and satellite provides and the online offering. We will delay the start of the main event slightly to allow for systems to get on track. We do not expect a lengthy delay," Showtime Sports said.