US inflation declined slightly last month as the cost of gas and groceries slipped, though prices are still rising more quickly than before the Iran war, posing challenges for the White House as the midterm elections near. Consumer prices increased 3.4 per cent in July from a year ago, down slightly from 3.5 per cent in June, the Labor Department said Wednesday. Inflation had fallen to 2.4 per cent before the Iran war. On a monthly basis, prices rose just 0.1 per cent from June to July.