The Allegiant Stadium - home of the Las Vegas Raiders - has been reserved by Top Rank for Tyson Fury and Deontay Wilder on July 24.
An arbitration court ruled the pair must fight for a third time by September 15.
It has put the fight between Fury and Anthony Joshua - scheduled for August 14 - in doubt.
The pair were expected to slug it out for all four major heavyweight world championships in Saudi Arabia.
Fury confirmed the news on Monday following a conversation with Saudi Arabia's prince.
Step aside money is not an option to move Wilder out of the way of the British blockbuster according to Bob Arum.
"We're not paying Wilder to step aside," Arum told ESPN.
"It's better to get rid of him and go about our business. We can make the Fury-Joshua fight for November or December."