Oleksandr Usyk has been ordered by the World Boxing Organisation to begin discussions over a mandatory defence of his heavyweight title against Joseph Parker.
The Ukrainian, currently the unified champion, retained his WBO, WBA and WBC titles with a unanimous decision victory against Tyson Fury at Riyadh's Kingdom Arena last December.
That came after Usyk relinquished his IBF title to Daniel Dubois last June, with the Briton previously due to defend it against WBO interim champion Parker in February.
However, the former withdrew at short notice through illness, and had been expected instead to bypass a rearranged fight in favour of an undisputed clash with Usyk.
Those plans have now been thrown into disarray by the WBO, who have instructed the latter to start negotiations with Parker instead, with 30 days to reach an agreement.
"Please be advised that the WBO World Championship Committee is hereby ordering the commencement of negotiations between to discharge the WBO mandatory championship obligation in the heavyweight division," read an official statement.
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"By virtue of this order, the WBO Interim Championship shall be terminated expeditiously in compliance with our institutional policy of only one world champion per weight class.
"The parties have 30 days to reach terms. Failure to do so will result in this committee ordering purse bid proceedings in accordance with WBO regulations of World Championship Contests."
Usyk and Dubois had been tipped to meet next, with Wembley Stadium mooted as a potential venue following the latter's ruthless win over Anthony Joshua there in September.
Parker, who stopped late replacement Martin Bakole inside two rounds after Dubois withdrew from their bout, is also pursuing another shot at a world title however.
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