More than 1,000 jobs at the electronics seller have already been cut across the 41 stores that have shut since it went into administration.
Around 70 Comet stores of the original 236 will remain open and continue to trade until all their stock has been sold, Deloitte said.
But the entire chain, which still employs around 5,000 staff, could close before Christmas unless Deloitte can find a buyer.
Should a takeover not materialise, then Comet would be the biggest retail chain to fall since Woolworths four years ago.
Comet's joint administrator Chris Farrington said: "We remain in discussions with a small number of interested parties and hope that a positive outcome can still be achieved.
"Should any acceptable offers be received for stores we will delay the closure process. Unfortunately, in the absence of a firm offer for the whole of the business, it has become necessary to begin making plans in case a sale is not concluded. If a sale is not possible we would envisage stores to begin closing in December."
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Deloitte has already announced the closure of Comet's distribution centre in Hadlow, and a reduction in headcount at the office functions at Hull, Rickmansworth in Hertfordshire, and Clevedon near Bristol.
Dixons Retail, owner of Currys and PC World, is understood to be in talks to buy some of Comet's stores. Appliances Online is said to want to buy the Comet brand and its online operation.