His announcement came just minutes after an official team spokesman had said that it would be a "tactical not medical" decision on whether Kanu would play - suggesting that the star had broken down while trying to recover too quickly.
Later, when the team returned to their hotel base, Kanu appeared to be walking freely but looked despondent.
Meanwhile, Ashley Cole today insisted the team are focused on the clash with Nigeria but believes they can go through to the knockout stage of the World Cup.
"Everyone knows how hot and tough it will be but everyone is focused on Nigeria. Everyone believes we can do it, the squad, the manager."
The Arsenal defender also spoke of his "proudest moment" following the 1-0 win over Argentina last Friday. He said: "I didn't think anything could beat the Germany victory but beating Argentina was the proudest moment of my life.
"Playing in the Premiership and the Champions League has been unbelievable but that topped everything."
Cole has a yellow card against his name but is determined not to hold back and said: "I will think about it if I am chosen for the game. But we need to get something from the match and I'll do anything to get that."
