The WBC has formally notified the camps of Tyson Fury and Deontay Wilder to arrange a rematch by February 5th.
The organisation also said Briton Fury is entitled to a bigger share of the purse for the bout due to his “market value”.
Fury and heavyweight champion Wilder fought out a controversial draw in Los Angeles in December.
Fury was twice knocked down, including once in the final round, but he had previously been the dominant fighter.
If both camps do not agree an acceptable fee by the deadline the fight is open to bids from other promoters.
A WBC statement read: “Consistent with the WBC board of governors voting regarding the direct rematch between WBC champion Deontay Wilder and Tyson Fury, the WBC is hereby notifying both camps that the free negotiation period is opened and if there is no agreement between the parties a purse bid will be conducted by the WBC on Tuesday February 5th.
“The WBC has modified the 70-30 split and has confirmed a 60-40 split in favour of the champion Wilder considering the market value of Fury.”
