A source close to the proposal told AFP on Tuesday that Qatari financier Sheikh Jassim bin Hamad Al Thani has increased his offer to buy Manchester United from the Glazer family.
The two men emerged as the leading candidates to acquire the Premier League heavyweights, and Sheikh Jassim is now engaged in a bidding battle with British billionaire Jim Ratcliffe.
When a third round of bidding ended last month, Ratcliffe seemed to be the front-runner.
Ratcliffe, the founder of the chemical giant INEOS, and a lifelong United supporter, allegedly valued the team higher because he wants to own a controlling ownership.
However, if he wins, executive co-chairmen Avram and Joel Glazer may continue to have a stake in the Red Devils, which would be very unpopular with fans.
Sheikh Jassim's offer, in contrast, calls for full ownership of the organization and pledges to pay off United's debt of $1.2 billion ($970 million).
When they originally solicited outside investment in November, the Glazers, who have failed to win over the supporters since they burdened the club with debt in a £790 million leveraged buyout in 2005, were ready to sell out at a huge profit.
Before they agree to sell, they are allegedly demanding a record-breaking £6 billion for a football club.
The Manchester United Supporters' Trust (MUST) has requested a speedy resolution of the matter so that the summer transfer window can begin with the new owners in place.
The Glazers' tenure as United's managers has seen a decline in the team's performance.
Since previous manager Alex Ferguson left his position ten years ago, they have not won the Premier League championship.
However, earlier this year, United did break a six-year trophy drought when they won the League Cup under new manager Erik ten Hag.