Asked in an interview with Stern magazine whether Germany would have triumphed with him in goal, Kahn replied: "Yes."
Kahn was player of the tournament in 2002, when Germany were runners-up, but a blunder in the final gifted Ronaldo the opening goal.
Lehmann performed exceptionally during the World Cup, particularly during the penalty shootout win over Argentina in the quarter-finals.
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The Arsenal goalkeeper's great rival was quick to emphasise he was not sniping, but based his assertion on a sequence of events throughout his career.
"That is not at all a criticism of Jens Lehmann. No, it is simply because of the way my career has progressed that I have this conviction," said Kahn.
"In 1994 I was knocked out of the UEFA Cup with Karlsruhe, then two years later won it with Bayern Munich.
"In 1999 I lost the Champions League final in the most brutal way, and then won it two years later.
"Unfortunately I played and lost in the 2002 World Cup final. I believe this logic, or rather this phenomenon, would have continued at the 2006 World Cup."
Kahn also revealed that he told Klinsmann of his theory before the World Cup but: "He didn't recognise this point - or didn't want to.
"I told him: 'I can't understand why you do not recognise it'."
Klinsmann's goalkeeping coach Andreas Koepke said Kahn's theory held no sway in team selection.
"Oliver's theory is an interesting one, but naturally there is no evidence to refute it. We did not pick the team at the World Cup based on phenomena."
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