Worried about higher ticket prices and loss of the club's British heritage fans' groups mobilized Monday to block any takeover by the multimillionaire Tampa Bay Buccaneers owner.
"If Glazer wants a fight we will give him one said Jules Spencer chairman of the Independent Manchester United Supporters Association. "We want to make it clear that he is not welcome or wanted as owner of Manchester United."
In a statement to the London stock exchange Manchester United's board said it had received a "preliminary approach" for a buyout of one of the world's richest and most successful sports franchises.
While the club didn't identify the potential bidder it is widely believed to be Glazer.
The statement was issued after weekend newspaper reports that Glazer appointed U.S. investment bank JP Morgan to advise him on a 600-million-pound (US$1 billion; euro871 million) takeover.
The statement said the 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 said.
Man Utd's share price jumped almost 4 percent to 267 pence (US$4.75; euro3.89) following the statement. The club is valued at around 700 million pounds (US$1.24 billion; euro1.01 billion).
Glazer already has a 19.2 percent stake in United. He's the second largest shareholder behind Irish racehorse owners J.P. McManus and John Magnier whose joint company Cubic Expression holds a 28.9 percent stake.
Glazer would have to buy the Irishmen's shares to gain control of the club. Any shareholder with a stake of 30 percent or more is required to make a formal takeover bid.
About 18 percent of the club's shares are held by small investors many of whom are hard-core fans opposed to a takeover by any single person or company.
Manchester United fans' groups wield significant influence. As a bloc they played a key role in foiling a takeover bid by Rupert Murdoch's BSkyB in 1999.
"Malcolm Glazer is an investor shareholder who wants to make a profit to suck the marrow out of Manchester United said Sean Bones chairman of Shareholders United. "It's up to every Manchester United supporter to do their best. Even if he does get enough shares we will have a foothold to repel him."
Glazer who has steadily increased his stake in the club over the past two years issued a statement in March saying his company Glazer Family Partnership had "no current intention" of launching a takeover.
Analysts said the club's current share price down from a high of 440 pence (US$7.83; euro6.40) could be considered a good buy.
The timing could also be motivated by the spectacular debut of 18-year-old striker Wayne Rooney who scored three goals in Man Utd's 6-2 Champions League win over Turkish side Fenerbahce last week.
Rooney who transferred from Everton to United over the summer in a deal worth up to 30 million pounds (US$53.4 million; euro43.6 million) is viewed as potentially the best English player of the era.
Manchester United claims 75 million fans worldwide more than half of them in Asia. The club has won the English Premier League title eight out of the last 11 years but finished third last season and is fourth this year.
Glazer who bought the Buccaneers in 1995 for US$192 million transformed the NFL team from a perennial loser into Super Bowl champions in 2003. The Bucs are 0-4 this season.
Glazer made his money in a variety of ways starting at age 15 when he took over the family watch business after his father died. Now he runs First Allied Corp. a conglomerate of businesses with an estimated worth of US$1.5 billion.
But Glazer isn't as wealthy as Roman Abramovich the Russian oil billionaire who took over London club Chelsea in June 2003. He cleared the club's multimillion pound debts and spent more than 200 million pounds (US$362 million; euro290.5 million) on new players.
Man Utd fans believe Glazer would have to borrow money to buy the club resulting in increased ticket prices.
Some fans also just can't stomach the idea of an outsider particularly an American owning the club.
"It's not that Mr. Glazer is American it's that he's never been to Old Trafford he doesn't have any understanding of the culture and the traditions and the heritage of football let alone Manchester United said Nick Towle of Shareholders United.
"It's very difficult for people like that to know how emotional fans feel about their club their heritage."