Wladimir Klitschko will attempt to regain the world heavyweight title by taking up his option for a rematch with new champion Tyson Fury next year.Briton Fury, 27, beat the Ukrainian in Dusseldorf, Germany, on Saturday to take the WBA, IBF and WBO belts.
The contract for the fight included a clause for a rematch, for which the date and the venue have to be decided.
"Failure is not an option," said Klitschko, 39, on his prospects of winning back the titles.
"I was really frustrated directly after the fight, but after some short nights, I now know that I am much better than my performance on Saturday.
"I couldn't show much full potential at any time. This is what I want to change in the rematch, and I will."
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Manchester fighter Fury said on Sunday that he would beat Klitschko again if they were reunited in the ring next year.
Fury's uncle and trainer Peter told BBC Radio Manchester it was "fantastic news" Klitschko had taken up the option.