Carrefour has reported a larger than expected €58m (£51.1m) loss in its first half, compared with a €747m (£655.7m) profit a year earlier.
The grocer plans to spend as much as €600m (£528.8m) on discounts and marketing this year to improve sales in France. Revenue fell 1.6% in the first half to €41.27bn (£36.37bn).
Chief executive Lars Olofsson said the retailer is on track to meet its 2009 targets, which include reducing inventory times by two days. Olofsson also revealed that a category review is under way in French hypermarkets, with the aim of simplifying and optimising the offer.