Wal-Mart said 'operating income was moderately below plan for the second quarter' because of 'declining margins from the competitive environment in the UK'.
Total sales increased by 'mid-single digits' for the quarter and like-for-like increases were in the 'low-single digits' - both above forecast.
The group said Asda's sales improvement was down to an increase in footfall and a better customer perception of price and stock levels.
The US-based company said it was encouraged by Asda's increase in market share during the quarter. TNS figures released last week show Asda's market share increasing from 16.4 per cent for the 12 weeks to May 21, to 16.6 per cent for the 12 weeks to July 16.
Asda has opened seven stores so far this year: two trial Asda Essential stores, one Asda Living store and four superstores.