Sir Alex Ferguson rejected the chance to sign Joe Hart

Manchester United boss Sir Alex Ferguson

Manchester United manager Sir Alex Ferguson has revealed his regret at passing up the chance to sign Joe Hart for £100,000 earlier in his career.

Hart, 24, joined Manchester City from Shrewsbury in 2006 and has become England's first-choice goalkeeper.

But Ferguson told BBC Radio 5 live: "I could have bought Joe Hart for £100,000 so we all make mistakes."

The Scot also said he would like an ambassadorial role at United after another "two or three years" as boss.

In a wide-ranging interview, the United manager claims Hart will be an England regular for at least another decade and is the best goalkeeper the country has produced for the last 20 years.

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Ferguson wants future United role

After struggling to replace Peter Schmeichel, who left Old Trafford in 1999, Ferguson eventually signed Edwin van der Sar from Fulham in 2005.

Van der Sar retired last summer and although Ferguson has defended the purchase of David de Gea, many United fans will be frustrated to hear that Hart could have been their player.

The United manager claims he could have picked the youngster up from Shrewsbury before he eventually moved to rivals City for an initial fee of £600,000 in 2006.

Ferguson said: "I've no doubt [that Hart will be England goalkeeper for the next 10 years].

"If you look at the England goalkeeper situation for the last 20 years, I would think he's easily the best."

Ferguson also spoke highly of former England and Tottenham midfielder Paul Gascoigne, saying that he was "the one that got away".

The Reds boss had the opportunity to sign the playmaker in 1988 when the 21-year-old was still at boyhood club Newcastle United, just before he joined Spurs.

"I would love to have signed Paul Gascoigne," Ferguson said. "I think I could have done something with him, he's the one real world star England have produced.

"Wayne Rooney and Steven Gerrard have come close but they don't have the genius of Gascoigne. He could have played for Brazil."

Under Ferguson's guidance, Manchester United have grown to become one of the most decorated club sides in the world, winning 12 domestic league titles and triumphing twice in the Champions League.

Ferguson was due to retire at the end of the 2001-02 campaign but had a change of heart.

And he seems to have been inspired to build the next great United side by the rise to prominence of Manchester City, whom he memorably described as "noisy neighbours."

"I think you always want to go out on a winning note," said Ferguson.

"Hopefully we can do that. I don't know how long I can last now but if my health stays up I don't think another two or three years would harm me."

He also says his wife is keen for him to remain active and has even suggested he becomes a milkman when he steps down as manager.

There has been constant speculation about who will succeed Ferguson, with a string of former players linked with the job at various times.

Ferguson himself is a long-time admirer of Real Madrid manager Jose Mourinho and believes the Portuguese would get more 'freedom' to do the job in England than he gets in Spain.

Mourinho was hugely successful at Chelsea and in December spoke of his desire to return to management in the Premier League.