Boxing legend Mike Tyson is backing Wladimir Klitschko to knock-out Britain\'s David Haye in Saturday\'s heavyweight unification bout and says the brash Brit lacks the fire-power to claim victory. Klitschko, 35, the IBF and WBO heavyweight champion, takes on WBA title-holder David Haye in Hamburg and boxing legend Tyson says the Ukrainian can knock the Brit out inside three rounds. \"David has never shown the punching power to force a guy of the caliber of Klitschko into reverse gear,\" Tyson, a former WBO, WBC and IBF champion, told German television channel RTL. \"We know that David Haye does not hit hard enough to get the respect of Wladimir Klitschko. \"I don\'t say this to disrespect Haye, but as an objective observer. \"I must say, this is a two or three-round fight.\" Tyson lost his last title bout to Britain\'s Lennox Lewis in June 2002, but at the peak of his career in the late 1980s, he held three of the four major belts. More than 1,000 fans turned up for Friday afternoon\'s weigh-in in Hamburg. Klitschko tipped the scales at 110kgs, significantly more than Haye\'s 96.5kg. There were several British fans in the crowd and shouts of \"Klitschko, who are you?\" and \"Klitschko is going down\" could be heard. In a sport well-known for trash-talk, this fight has seen a particularly aggressive war-of-words with Haye insisting he will shake Klitschko\'s hand only when he visits him in hospital on Sunday. In reply, Klitschko branded the Brit\'s comments \'disrespectful and disgraceful\'. \"It is the fight of the century,\" said Haye. \"I\'m in the shape of my life and have reached the ideal weight. \"Wladimir will lie at my feet in the ring.\" Klitschko just repeated his desire to make Haye the 50th knock-out of his career. \"I am looking forward to the fight. It will be my 50th KO win,\" he said. Klitschko has won 55 of his 58 bouts, while most of Haye\'s 25 wins from 26 fights have come at cruiserweight after he stepped up to heavyweight in 2008. Both fights suffered their last defeat back in 2004, but if Klitschko wins to claim Haye\'s WBA belt, it will be the first time in history one family has held all four major belts as brother Vitali is the WBC champion.