* Expect improved bids for 48.3 percent stake by March 31
* Ready to sell a 25 percent stake
(Updates with owners' comment)
LJUBLJANA, March 11 (Reuters) - The two biggest shareholders in Mercator have asked bidders for their combined 48.3 percent stake in Slovenia's largest food retailer to improve their offers by March 31,
"We also informed the bidders that we would be ready to sell also only (a) 25 percent stake in Mercator and not necessarily the whole 48.34 percent stake," Slovenian beverage producer Pivovarna Lasko said in a statement.
Pivovarna Lasko owns a 23.3 percent stake in Mercator, while investment fund Infond Holding owns 25 percent. The pair said in November they wanted to sell their holdings and in December set Feb. 2 as the deadline for non-binding bids.
Pivovarna Lasko denied a report in the Dnevnik newspaper that it and Infond had decided to sell just a 25 percent stake in Mercator, Slovenia's fourth largest listed company with a market capitalisation of 563.5 million euros ($715 million).
Dnevnik also reported there were seven bidders for Mercator and the owners expected to sell their shares well above the market price and above prices offered by the bidders.
Infond and Pivovarna Lasko have not given any detail on the bids they received for Mercator. So far only Serbia's biggest food retailer Delta Holding has said it submitted a bid.
Mercator, which owns stores in Slovenia, Bosnia, Croatia, Montenegro and Serbia and plans to enter Bulgaria this year, would not comment.
Its shares were down 0.4 percent to 146.20 euros at 1010 GMT, while the blue-chip SBI index was up 2.2 percent. (Reporting by Marja Novak; Editing by David Holmes and Dan Lalor) ($1 = 0.7881 euro)