By Veronica Ek and Jessica Wohl STOCKHOLM/CHICAGO (Reuters) - Major U.S. retailers, including Gap Inc, declined to endorse an accord on Bangladesh building and fire safety backed by Europe's two biggest fashion chains, a trans-Atlantic divide that may dilute garment industry reform efforts. Three weeks after the collapse of a building housing garment factories, which killed more than 1,100 people, Western brands that rely on Bangladesh to produce clothing cheaply disagreed over how best to ensure worker safety. ...