Oleksandr Usyk

Anthony Joshua v Oleksandr Usyk confirmed for Tottenham on 25 September

Joshua, 31, will risk his IBF, WBA and WBO belts against the Ukrainian, who is his mandatory challenger.

Usyk, 34, has not fought for a title as a heavyweight but held all four belts a division lower at cruiserweight.

Joshua was ordered to defend his WBO title after the collapse of his bout with fellow Briton Tyson Fury.

"We are two Olympic gold medallists who have fought our way to the top and never avoided challenges," Joshua said.

Joshua or Fury Both, says Usyk

Fury completed a stunning seven-round demolition of knockout specialist Deontay Wilder in Las Vegas last month to collect the WBC title, while countryman Joshua holds the other three major heavyweight belts after avenging his defeat to Andy Ruiz with a comprehensive points win last December.

Usyk, who is like Fury undefeated and has a London 2012 gold medal in common with Joshua, cleaned out the cruiserweight division and has similar designs having stepped up to take on boxing's big men.