Sainsbury's and Asda, the two British supermarkets that want to combine their businesses, have asked for a delay in the competition inquiry into their proposed £7.3 billion (€8.1 billion) deal.
A deal between second-ranked Sainsbury's and the British arm of Walmart, the number three player, could see the combined group leapfrog Tesco as market leader and is being assessed by the Competition and Markets Authority (CMA).
Sainsbury's and Asda said the current timetable did not give them, or the CMA, sufficient time given the unprecedented scale and complexity of the case.
The CMA expects to issue provisional findings of its investigation early next year ahead of a final report in March.
Request For Additional Time
Sainsbury's and Asda said they had engaged constructively with the CMA and had made repeated requests for additional time, specifically an extra 11 working days over Christmas to respond to a large amount of material recently provided.
"This is a case of unprecedented size and complexity and we have a responsibility to our customers and colleagues to ensure that we and the CMA have enough time to make and consider all the facts and evidence," a spokeswoman for both supermarkets said.
"This is not a decision we have taken lightly. It is about ensuring a thorough process and reasonable timetable. We remain confident in the case for merging the businesses and the significant customer benefits."
Tesco has said the deal should not be cleared without 'extensive remedies', and number four Morrisons has raised concerns about an 'effective duopoly' - Tesco and Sainsbury's-Asda - controlling in excess of 60% of the market.
Sainsbury's and Asda said they would lodge an application with the Competition Appeal Tribunal later on Wednesday for a Judicial Review of the CMA investigation into their proposed merger.
Shares in Sainsbury's were trading down 3.3% at 286.5 pence in early deals.