Advisers to CVC and its private equity partners approached J Sainsbury with details of its cash offer on Monday, The Times has learnt.

It is understood that Monday’s talks were at a very early stage and the retailer has not yet opened its books for due diligence.

Senior executives at Sainsbury’s, however, are understood to expect the situation to come to a head within the next 48 hours.

CVC is bidding with Blackstone, Texas Pacific Group, KKR and Goldman Sachs for Sainsbury’s, which is valued at £9 billion excluding debt.

At Monday’s meeting CVC revealed draft details of its takeover plan, including giving an indication of price, understood to be above 550p a share.

That would value the supermarket chain at £9.5 billion, although no firm price has been put on the table, the sources said.

“They’ve had verbal conversations so far,” one source familiar with the discussions said, adding that the group had not yet submitted a formal proposal.

Last week Sainsbury’s asked the Takeover Panel to issue a “put up or shut up” notice to the consortium, which forces it to bid or walk away by April 13.

The CVC-led group initially said it was considering a bid, which would be Europe’s biggest buyout, on February 2.

Since then Sainsbury’s share price has risen as much as 22 per cent, to a record last week of 544p.

Investors including the property entrepreneur Robert Tchenguiz have snapped up the retailer’s shares, which closed off 2.2 per cent yesterday at 521p.

People close to the CVC group have argued that it will be difficult for the consortium to proceed with a bid, given the rise in the share price.

The backlash against the private equity industry by unions is also making buyout firms cautious.

“The PR aspect of this has become huge,” the source said. “That’s why this has taken a lot longer.”

It is understood that the CVC group wants clarity on issues such as Sainsbury’s pension deficit, before embarking on a full-blown bid.

It fears making an offer and getting a public rejection from Sainsbury’s, in the same way that Alliance Boots knocked back a potential £10 billion bid from KKR earlier this week.

At the same time, Sainsbury’s wants more detail on the capital structure of the bid and plans for the financing of its property portfolio.