Reports suggest that billionaire Sir Jim Ratcliffe is exploring the idea of altering his bid to acquire a minority stake in Manchester United.

Ineos founder Ratcliffe, who had attempted to buy Chelsea last year, joined the race to purchase United in January and had been the sole bidder before Sheikh Jassim entered the running a month later.

A lengthy takeover saga has followed with numerous bids entered by both boyhood fan Ratcliffe and Sheikh Jassim, but no progress has been made over any potential change of ownership from the Glazer family, who announced in November they were open to selling the club.

Manchester United's valuation on the New York Stock Exchange plummeted by over 500 million pounds ($604 million) last month in the wake of reports the Glazers may not sell.

It is now being reported that Ratcliffe, the second-richest person in the U.K. according to the Sunday Times Rich List, could decide to buy a minority stake in the Premier League giants.

Sky News reported Ratcliffe may seek a stake in the region of 25% as part of a proposal to try to bring the drawn-out sale process to an end, having initially wanted to complete a majority takeover.

If the Glazers accepted this newly reported offer, it would see the American family still retain majority control of the club they first bought in 2005.

United fans have protested against the Glazers for years and thousands took part in an hour-long sit-in at Old Trafford after a 3-2 win over Nottingham Forest in August.

It has been 18 years since the Americans' controversial leveraged takeover and over 10 months since they announced a strategic review.

Ratcliffe's team declined to comment when contacted.