Sir Alex Ferguson has claimed he will retire if he can win "a couple more European trophies" with Manchester United.
In an interview with CNN, Ferguson conceded that United should have enjoyed more success in Europe than the two Champions League titles in 1999 and last season.
"If there was one challenge I'd love the club to win more European trophies than they have done and I think I've made this point a few times over the years. I don't think we've won the number we should have won," he said.
"There have been years when we've been unlucky and years we've been disappointed, and there've been years when we've thrown games away, and that sort of gives a kaleidoscope of what football's like.
"If we could win a couple more European trophies I then would definitely quit."
Ferguson also spoke about star winger Cristiano Ronaldo, praising the 24-year-old for the maturity he has developed in avoiding the temptations that come with his high profile.
"I think that he's had temptations and I think there have been periods when you've seen the effect of it (on the pitch)," Ferguson said.
"He's lucky in the sense that people here can tell him the truth and be straight with him and he appreciates that, and he has responded to that.
"If it stays with him and changes him as a person then you have a problem.
"Fortunately Ronaldo has good human qualities. He's a good guy. He knows when he's gone too far and he draws back in after that."
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