A final decision by Tesco could mark the end of a three-way tussle for control of the company's Thai operations, which comprise some 2,000 stores, said the sources, who declined to be identified as the information is confidential. Sources have said Tesco is also selling 74 outlets in Malaysia.

The bidding is shaping up as a battle between Dhanin Chearavanont's Charoen Pokphand (CP) Group, Central Group, controlled by the Chirathivat family, and beer-and-property magnate Charoen Sirivadhanabhakdi's TCC Group, sources said.

"The end game is near," said one banking source.

The three Thai groups did not immediately respond to a Reuters request to comment on Sunday. Tesco also did not immediately respond to a request for comment.

Three sources said bidders were given until Sunday to come up with any last-minute revisions to their bids.

They said CP Group, which had sold its supermarket chain to Tesco during the Asian 1997-98 financial crisis, was the frontrunner.

Britain's biggest retailer said in December it started a review of its Asian operations, made up mainly of the Thai and Malaysian operations, after receiving interest.

Sources have also said antitrust concerns could pose a challenge to bidders as Thailand's antitrust office said last month that the deal should not violate anti-monopoly laws.

The Financial Times reported earlier on Sunday that Tesco's board was set to meet this weekend to finalise plans to sell the UK supermarket chain's Thai and Malaysian operations.

(Reporting by Anshuman Daga in Singapore and Kane Wu in Hong Kong; Additional reporting by Chayut Setboonsarng in Bangkok. Editing by Jane Merriman)

By Anshuman Daga and Kane Wu