Jermell Charlo anticipated a swarm of mandatory title defenses to come into play the moment he was crowned undisputed champion.

The first one is officially on the clock.

Houston’s Charlo has been ordered to next defend his undisputed junior middleweight championship versus WBO mandatory challenger Tim Tszyu. Both fighters and their respective camps were formally informed Tuesday morning to begin the negotiation process for their forthcoming title fight.  

“Please be advised that the parties have twenty (20) days upon receipt of this letter to reach an agreement,” Luis Batista-Salas, chairman of the WBO Championship Committee informed both parties via official letter, a copy of which was obtained by “If an accord is not reached within the time frame set forth herein, a Purse Bid will be ordered pursuant to the WBO Regulations of World Championship Contests.”

Charlo (35-1-1, 19KOs) inherits the mandatory title defense previously intended for then-unbeaten WBO junior middleweight titlist Brian Castano (17-1-2, 12KOs).

Both fighters were made aware of Australia’s Tszyu (21-0, 15KOs) being next line, as the WBO notified both boxers and TGB Promotions’ Tom Brown of the ruling in a May 9 letter that formally confirmed the WBO’s sanctioning of their May 14 undisputed championship rematch. Charlo entered the fight as the lineal/WBC/WBA/IBF champ, adding the WBO strap following a tenth-round knockout of Castano at Dignity Health Sports Park in Carson, California.

The fight came ten months after the two fought to a disputed twelve-round, split decision draw last July 17 in San Antonio, Texas. Several delays in getting the rematch over the line created a backlog of mandatory challengers in waiting, including IBF number-one contender Bakhram Murtazaliev who has been paid step-aside fees and granted non-televised undercard slots on PBC shows in exchange for waiting his turn to fight for the crown.

Tszyu wasn’t as patient. The unbeaten second-generation boxer and his promoter, No Limit Boxing, pushed for his mandatory status to be enforced earlier this year once Charlo-Castano II was officially postponed from its March 19 date after Castano suffered a training camp injury. The WBO fielded requests from Tszyu, No Limit and TGB before making a ruling that would allow the rematch to proceed on the condition it took place no later than May 14 and that the winner agreed to face Tszyu no later than 120 days from that point.

Sweetening the pot, PBC signed Tszyu to a multi-fight deal that began with his off-the-canvas, twelve-round points win over Terrel Gausha this past March 26 in Minneapolis, Minnesota. The Showtime-televised event marked the U.S. debut for Tszyu, whose father Kostya is a Hall of Fame former undisputed junior welterweight champion.

Tszyu has remained adamant of his next fight being for the division’s ultimate prize.

“He’s got four months to decide if that fight’s going to happen or if he vacates,” Tszyu previously told “If he decides to vacate then I’ll fight for the WBO title, which means—I don’t know exactly how that will work, whoever is next in line, I suppose.”

Should the fight head to a purse bid hearing, the minimum acceptable bid is $200,000. Either side can request a purse bid hearing at any point during the ordered negotiation period.

Jake Donovan is a senior writer for Twitter: @JakeNDaBox