The Qatari group seeking to take over J Sainsbury, Britain's third-largest grocer, faces a Nov. 8 deadline to make a firm offer or withdraw, the parties said Friday.
They also disclosed that the Qatar-based Delta Two is seeking 500 million pounds (720 million euros; $1 billion) of additional equity to bolster its 600-pence per share offer for Sainsbury.
The offer values the company at 10.6 billion pounds (15.2 billion euros; $21.7 billion).
Sainsbury and Delta Two agreed to apply to London's Takeover Panel to set a deadline. If Delta Two cannot meet the deadline, it will be barred from making another offer for Sainsbury for six months.
"Delta Two has entered into discussions with the Qatar Investment Authority to secure such funding," the parties announced. "There can be no certainty that such funding will be forthcoming and, therefore, no certainty that an offer will be made."