The firm, which revealed last week that it had a November bid approach for Argos owner Home Retail rejected, said sales at stores open over a year fell 0.4 percent, excluding fuel, in the 15 weeks to Jan. 9, its fiscal third quarter.
That compared to analysts' average forecast of a fall of 0.7 percent and a second quarter decline of 1.1 percent.
Sainsbury's said it now expects its like-for-like sales in the second half of the year to be better than the first.
Previously it had expected a similar performance.-Reuters