Lennox Lewis has dismissed a possible fight against WBO heavyweight champion Wladimir Klitschko as a "waste of time." Lewis, 36, who beat Mike Tyson last month to retain his WBC and IBF titles, said he had no interest in fighting Klitschko, a former Olympic gold medalist from the Ukraine. "Vladimir Klitschko, he's not tough enough," Lewis said in London. "It would be a waste of my time to go and fight him. I will knock him out." Lewis could be stripped of his IBF title if he does not fight No. 1 challenger Chris Byrd.