Qatari-based investment firm Delta Two has confirmed that it has entered into an agreement to exchange information with Sainsbury's pension trustees.
The news comes after the supermarket chain revealed last week that it was opening its books to the investment fund.
Delta Two, which has tabled a proposed £10.6 billion bid for Sainsbury's, said that the two parties had signed a non-disclosure agreement in order to swap confidential information about the potential impact that a deal would have on the retailer's pension schemes.
The investment group said the exchange was necessary in order for it to formulate an appropriate pension proposal to put before Sainsbury's trustees.
A further statement will be made on the matter in due course, said Delta Two.
Paul Taylor, Delta Two's strategic investment adviser, said: "Delta Two recognises the importance of ensuring that the Sainsbury's pension schemes are appropriately funded and intends to work constructively with the trustees to reach a timely agreement on the appropriate level of funding for the schemes."
John Adshead, chairman of Sainsbury's pension trustees, said: "I am pleased that the trustees are now able to engage in detailed discussions with Delta Two regarding future funding of the Sainsbury's pension schemes.
"We, the trustees are clear that our responsibility is to ensure that the benefits earned by members of the pension schemes are properly funded and secured," he added.
Delta Two, which already holds a 25 per cent stake in Sainsbury's, previously revised the terms of its planned offer for Britain's third-largest supermarket group. Although the investment group is still considering making a bid for the retailer at 600p a share, less of the proposed bid is now funded by debt.
The supermarket's board has suggested that such a bid could be recommended to shareholders, but to mount a successful takeover of the company Delta Two will need to win the backing of the Sainsbury's founding family. The family, who own an 18 per cent stake in Sainsbury's, previously opposed an approach from a consortium of private equity firms led by CVC.