A group of financiers - dubbed the "Red Knights" - have met for the first time to discuss taking over Manchester United, BBC Sport understands.
United are owned by the Glazer family, but the club's high level of debt - now at £716.5m - has prompted much unease.
Goldman Sachs economist Jim O'Neill, who was acting in a personal capacity, lawyer Mark Rawlinson and financier Keith Harris were at the meeting.
A spokesman for the Glazers told BBC Sport: "United is not for sale."
However, United's owners are now facing a two-pronged attack over their control of the club with the Manchester United Supporters' Trust (MUST) running a vocal campaign to bring about a change of ownership.
http://newsimg.bbc.co.uk/shared/img/o.gif606: DEBATE
The green and Gold campaign has really had a BIG impact, its got them worried, but it was never meant to get rid of them
Stretford_Ender85
MUST has recruited 53,520 members and recently started working with Blue State Digital, a communications agency that worked on Barack Obama's successful US Presidential election campaign.
Their "Green and Gold" campaign has seen supporters don the colours of Newton Heath - the club was renamed Manchester United in 1902 - with plenty of green and gold scarves in evidence at Sunday's Carling Cup final.
The City financiers insist that their initiative is about changing the owners and that they have complete confidence in chief executive David Gill and manager Sir Alex Ferguson.
The "Red Knights" group also accepts that any takeover would have to be agreed by the Glazers, but that the club's American owners cannot prevent them from putting forward a proposal.
The financiers are also understood to want supporters to play a key role in their campaign.
According to the latest accounts that were released in January, debts at United's parent company Red Football Joint Venture have increased to £716.5m.
http://newsimg.bbc.co.uk/media/image..._banner226.jpg Man Utd fans have staged 'green and gold' protests against the Glazers
Red Football Joint Venture is owned by the Glazer family and secures its debts against the football club, but the accounts also confirmed that six of Malcolm Glazer's children were each given loans worth £1.67m from the parent company.
All are directors of Red Football, and such a practice is legal, but Harris, who is the head of merchant bank Seymour Pierce, has said it did "not create a good impression of the directors' governance of the company".
On Sunday, United beat Aston Villa 2-1 in the Carling Cup final to give Ferguson his 34th trophy with the club.
The "Red Knights" are due to release a statement on Tuesday.
