Man Utd owners await revised offers for Premier League giants
Reports said bidders were initially told they had until 2100 GMT on Wednesday to submit new bids, but that has now been extended.
It is unclear when the new cut-off will be.
Sheikh Jassim Bin Hamad Al Thani, the chairman of Qatar Islamic Bank, and Ratcliffe, the founder of chemicals giant INEOS, are the only bidders who have gone public with their intentions.
A first round of bidding took place last month and it has been reported there are as many as eight separate potential investors for the club owned by the American Glazer family, who are deeply unpopular with United supporters.
The BBC said several other proposed investors made their submissions by the Wednesday deadline.
No figures have been revealed but one or more of the initial bids was understood to be in the region of £4.5 billion ($5.5 billion).
That would make Manchester United - who have not won the Premier League for a decade - the most expensive sports club in history, although it would be short of the £6 billion valuation reportedly placed on United by the Glazers.
United's owners announced in November they were conducting a strategic review, with the sale of the club one option being considered.
Sheikh Jassim is bidding for 100 percent control, aiming to return the club to its "former glories".
A source close to Sheikh Jassim's bid told AFP he remains confident his bid is "the best for the club, fans and local community".
'Stupid prices'
INEOS chemical company founder Ratcliffe, a boyhood United fan, wants to buy the combined Glazer shareholding of 69 percent of the 20-time English champions.
The 70-year-old told the Wall Street Journal this week he was not interested in paying "stupid prices" in a bidding war for one of football's most iconic clubs.
Ratcliffe, who already owns French club Nice, said his interest in United would be "purely in winning things", calling the club a "community asset", rather than a financial one.
The Glazers have angered many United fans by saddling the club with huge debts since they took over in 2005. They appeared ready to cash out at an enormous profit when they invited external investment in November.
However, they could yet shun the option of selling a controlling stake in the club, with other parties understood to be interested in a minority shareholding.
Ratcliffe visited Old Trafford last week along with INEOS representatives, a day after a delegation from Sheikh Jassim's group toured the club's stadium and training ground.
A Qatari purchase of United would boost the sporting profile of the Gulf state months after it hosted the 2022 World Cup, but it would also be controversial.
Sheikh Jassim is the son of a former Qatari prime minister, raising concerns over the potential growth of state influence in the Premier League.
Premier League champions Manchester City's fortunes have been transformed since a takeover from Sheikh Mansour, a member of Abu Dhabi's ruling family, in 2008.
In 2021, the Saudi sovereign wealth fund bought a controlling stake in Newcastle.
Amnesty International has called on the Premier League to tighten ownership rules to ensure they are "not an opportunity for more sportswashing".
If Sheikh Jassim's bid succeeds, it would also raise the question of whether Qatar is shifting its attentions away from Paris Saint-Germain, currently home to the trio of Lionel Messi, Neymar and Kylian Mbappe, who were bought by Qatari investors in 2011.
United, three-time European champions, have not won the Premier League since Alex Ferguson led them to a 20th English title in his final season before retiring in 2013.
But they are enjoying a renaissance under Erik ten Hag's management this season and ended a six-year trophy drought by lifting the League Cup last month.
