The WBC has set a deadline of Feb. 5 for Deontay Wilder and Tyson Fury to agree to terms for a heavyweight rematch.
A "direct rematch" was sanctioned by the WBC after American Wilder and Brit Fury's controversial draw in Los Angeles on Dec. 1.
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Talks between the two camps have been held and the organization on Wednesday said that an agreement must be reached by early next month.
The WBC also revealed that the purse split has been modified from 70-30 in Wilder's favor to 60-40.
A WBC statement said: "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 favor of the champion Wilder considering the market value of Fury."
Fury revealed that he wants a homecoming fight against Wilder in April, but will face another opponent if that cannot be finalized.