By Steve Kim

The purse bid for the IBF welterweight title fight between world champion Kell Brook (36-1, 25 KOs) and top rated challenger Errol Spence (21-0, 18 KOs) was scheduled for Tuesday, but a seven day extension has been granted by the organization to allow promoters Eddie Hearn [for Brook] and Tom Brown [for Spence] the opportunity to make a deal on their own.

This much is clear: for Brook to keep his title he must face Spence next, regardless. The sanctioning body will not approve any exceptions or even a unification.

"(Brook) has to fight Spence, he can't ask for an exception or a unification,'' explained Lindsey Tucker, the Championship Chairman of the IBF, to BoxingScene.com. "Once we call for the purse bid then he can't do anything else. He can give up the title but he can't ask for an exception to fight anybody other than Spence."

Spence will get his long awaited title shot in his upcoming fight - with or without Brook. If Brook decides to vacate to purse another another path for his career, the sanctioning body will go down the rankings and select the highest available challenger. That initially would have been Jeff Horn, but the Australian Olympian is now heading to a world title shot against WBO champion Manny Pacquiao in April.

"If Brook for whatever reason decided to vacate the title, Spence would fight the next available highest contender," confirmed Tucker. "[Horn is] not available as far as we know, that fight [with Pacquiao is] pretty much a done deal."

So with that said, Spence would then be paired with former welterweight champion Andre Berto, who is rated number three by the IBF. Berto has been out of the ring since last April's TKO win over Victor Ortiz in their rematch.

Steve Kim is the news editor for BoxingScene.com.