The company saw like-for-like sales excluding fuel rise 5.1 per cent in the 12 weeks to June 16 - below some analysts' predictions of around 5.5 per cent.
The performance comes a day after Tesco disappointed the City with like-for-like sales growth of 4.7 per cent.
Sainsbury's said the recent round of price-cutting by Tesco, Asda and Morrisons reflected the competitive nature of the market, but added that it had moved to cut prices on 4,500 products since April.
Sainsbury's, the UK's third largest supermarket chain, reported its 10th successive quarter of growth, although today's figures compares with growth of 5.9 per cent in the previous quarter, and 5.7 per cent in the same period last year.
But chief executive Justin King said the company was up against tough comparatives, after last year's sales figures were bolstered by the World Cup and warmer weather.
He added that the company's sales performance was helped by control of stock levels during warm weather in April followed by a wet May, due to supply chain improvements.
Sainsbury's quality food sales drove growth, with increases in growth of Fairtrade and organic goods. By August, the company expects all bananas sold in its stores will be Fairtrade.
The firm boosted its green credentials in April with the launch of its reusable "bags for life" for customers, which it estimates will save 520m disposable carrier bags this year.
The company is in the final year of a three-year recovery plan begun by Mr King in 2004.
In May, it reported underlying profits up 42 per cent to £380m, and set out plans to grow sales at the business by £3.5bn within three years.
A £10.1bn bid from a private equity consortium for the company collapsed in April after opposition from the Sainsbury family, but investment fund Delta Two has recently built up a big stake and is said to be poised for a bid.
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