Sources close to the deal state that final due diligence threw up previously unknown liabilities which are set to cost United £10m between now and April.
"Upon completion of due diligence by our potential funders, the true scale of Leeds United's debt and liabilities have become clear," said Sainsbury last night. "It was obviously more than we, they, and many others had envisaged."
Sainsbury is hoping to construct a new proposal with secondary funders who had been informed of their position as a contingency in the event of a collapse of the first bid.
It is understood these backers, whose identity is unknown, have so far pledged to continue the takeover and it is anticipated that £2.5m can be drafted into a lawyer's account within five working days.
If the second funders pursue their interest in the bid and Leeds find the approach acceptable, sources say the takeover could be completed within 10 days.
"We do have a possible contingency plan," said Sainsbury. "Over the next 24 hours we shall be considering our options. There's no way I want to see (Leeds) go into administration, but should that happen I will not try to rescue it."