Sheikh Jassim bin Hamad Al-Thani has made an improved bid to buy Manchester United, sources have told ESPN.

Amid speculation that current owners the Glazer Family are favouring an offer made by British billionaire Sir Jim Ratcliffe, Sheikh Jassim has returned with another bid more than two weeks after Raine Group, the merchant bank handling the process, asked for final proposals to be submitted.

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An offer made by Ratcliffe, chairman of chemical company INEOS, in the third round of bidding placed a higher value on United than the previous bid from Sheikh Jassim and also included plans for siblings Joel and Avram Glazer to remain as shareholders.

Sources told ESPN it had made Ratcliffe the favourite to complete a takeover before Sheikh Jassim upped his offer.

His proposal is for 100% of the club and includes a separate fund to redevelop Old Trafford and improve the playing squad. The Qatari offer also promises to remove all debt racked up over 18 years of Glazer ownership.

The Glazers announced in November that they would look at "strategic alternatives," which could include accepting investment or a full sale.

In addition to the bids from Sheikh Jassim and Ratcliffe to buy the club, Raine Group has also received offers for a minority stake from a number of U.S.-based investment groups including Elliott Management, Ares Management, Sixth Street and Carlyle.

The next stage of the process is for Raine to name a preferred bidder to enter a period of exclusivity, which would grant the chosen party further access to the club's financials.

Earlier this year, club staff was told to expect clarity on the ownership situation by the end of the season, but that deadline is now only a little over two weeks away.