The World Boxing Organization has issued an official ruling, pursuant to a petition filed by attorney John Hornewer, to name Oleksandr Usyk as the mandatory challenger in the heavyweight division.

The current WBO heavyweight champion is Andy Ruiz, who also holds the WBA, IBO, IBF world titles.

Ruiz captured the belts on June 1, with a seventh round stoppage of Anthony Joshua in a shocking upset at Madison Square Garden in New York City.

A rematch is contracted between Joshua and Ruiz, with the second fight scheduled to take place before the year is over.

Ruiz's big win was a stumbling block for Usyk, who signed on with promoter Eddie Hearn - with the sole goal of facing Joshua for the unified crown.

Usyk was scheduled to make his heavyweight debut last month against Carlos Takam. He withdrew with an injury. His heavyweight debut is slated to take place in the coming months, possibly still against Takam.

In 2018, Usyk unified the entire cruiserweight division by winning the World Boxing Super Series cruiserweight tournament to unite the WBO, IBF, WBA, WBC world titles.

He last fought in November, when he knocked out and retired former world champion Tony Bellew.

The WBO's decision had some resistance, because Dillian Whyte is the top rated boxer in the weight class - and he wanted the sanctioning body to delay a ruling until July 22 - two days after Whyte faces Oscar Rivas in London.

Whyte appears to be in hot pursuit of a mandatory shot against WBC champion Deontay Wilder. Whyte has been the WBC's top rated challenger for nearly 600 days.

And the WBO argued that Usyk's status as the "super champion" at cruiserweight has given him enough merit to step over Whyte.