Weekend press reports suggested that multi-millionaire Glazer, who holds a 19.2-percent stake in the club, was poised to launch a takeover bid for the English giants, worth at least 650 million pounds (943 million euros, 1.17 billion dollars).

"The Board of Manchester United PLC notes the recent press speculation," the company said in a statement.

"It confirms that it has received a preliminary approach regarding a possible offer for the company. This approach contains a number of significant conditions.

"The company is seeking clarification of this proposal and at this stage it is unclear whether any offer will be made," it added.

In London, the price of shares in Manchester United jumped 3.40 percent to 266 pence, valuing the virtually debt-free club at 697.4 million pounds.

There was no immediate response from Glazer, owner of NFL franchise Tampa Bay Buccaneers, and the second-largest shareholder in United, whose fans number in millions from Manchester to Macau.

An analyst at Barclays Stock-brokers, Henk Potts, said the main attraction for Glazer would be to leverage marketing opportunities from the United brand, particularly in the United States, where the club signed a commercial tie-up with the New York Yankees baseball team in 2001 to market United merchandise.

"The club has been able to manage the great balancing act of being able to perform on the pitch as well as produce returns for shareholders," Potts added.

The Mail on Sunday newspaper said Glazer had hired investment bank JP Morgan to advise him on a bid worth "at least 650 million pounds".

Glazer was expected to seek the support of United's major shareholders, Irish racing tycoons John Magnier and JP McManus, who own 28.9 percent via their Cubic Expression company, the report added.

The pair have not bought any shares in Manchester United since February, stopping just short of the 29.9 percent threshold above which an offer to buy out the club would have to be made under British takeover rules.

Britain's Daily Star on Sunday newspaper meanwhile quoted top banker Mehmet Dalman, who has helped Glazer snap up his existing United shares, as saying that "the Glazer family -- Malcolm and his sons Joel, Ed and Bryan -- are interested in having a major involvement in United.

"The Glazers want to own the club -- either through buying more shares or through management or board level."

Manchester Untied fans voiced anger at the prospect of Glazer winning control.

"Supporters feel very strongly that they do not want Malcolm Glazer to take over," said Mark Longden, of the Independent Manchester United Supporters Association.

"He does not have the money to buy the club and would have to borrow heavily. The fans do not want the club to go into debt. It is a very risky business."

In 1999 the British government blocked a 623-million-pound takeover bid for United by the satellite broadcaster BSkyB, although supporters' opposition was seen as playing a key role for the failure.

Manchester United last week reported a near 30-percent fall in annual profits, hit by a weaker performance on the pitch, and warned that future results would be affected by a drop in media revenues.

The group saw pre-tax profits slide to 27.9 million pounds in the 12 months to the end of July from 39.3 million in the previous financial year.

United endured a disappointing last season by their own very high standards, finishing third in the English Premiership and exiting the lucrative European Champions League tournament before the quarter-finals stage.

In a bid to turn around fortunes on the pitch, the club splashed out 27 million pounds on England's teenage striker Wayne Rooney during the summer.

Rooney, 18, bought from Premiership rivals Everton, scored a remarkable hattrick on his United debut against Turkish champions Fenerbahce in the Champions League last week.

Off the field, United plan to increase the seating capacity at their Old Trafford stadium by 7,800 seats to 75,600.