Joshua won his rematch with Andy Ruiz Jr last weekend after sweeping the scorecard with a unanimous 118-110, 118-110, 110-109 verdict to reclaim the WBA, IBF and WBO belts that he lost to the Mexican in NY.
Whyte was added to the card just weeks earlier, although his doping case had yet to be resolved.
Whyte won the title on July 20 by beating Colombian Oscar Rivas but the WBC provisionally suspended recognition of his status as interim champion 10 days later over an irregular urine sample he had provided out-of-competition in June. However, Whyte was allowed to fight by British regulators despite having failed a drug test during the week of the fight.
On Wednesday, the WBC also cleared Whyte and reinstated him.
"Consistent with the WBC board of governors' ruling at last October's 57th WBC Annual Convention, interim champion Whyte shall become the mandatory challenger of the division immediately after champion Deontay Wilder's mandatory defence against current mandatory challenger Tyson Fury, with the mandatory defence against Whyte being due on or about February of 2021".
An undisputed battle for the title with the WBC champion, Deontay Wilder, remains Joshua's greatest ambition, who received new encouragement from WBC president Mauricio Sulaiman, in his quest for the last important belt.
The WBC said it found no sufficient or conclusive evidence that Whyte intentionally took a banned substance with the aim of enhancing his performance.
"In light of the WBC's own finding and the withdrawal of UKAD charges against Mr. Whyte, the WBC has closed its internal investigation".
A letter sent to Joshua's promoter Eddie Hearn from WBO reads:"The WBO World Championship Committee hereby orders the parties herein commencement of negotiations for the above-mentioned WBO heavyweight mandatory championship contest", the WBO wrote in the letter, a copy of which was obtained by ESPN.
Joshua says he will fight either the WBO's mandatory challenger - now Ukraine's Oleksandr Usyk - or the man in the same position with the IBF, Bulgarian Kubrat Pulev next.
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