...+ U.S. telecommunications provider AT&T lowered its revenue guidance for 2014 to 3%-4% from its previous 5% because of sluggish growth in its wireless segment. + It also announced that it would acquire Mexican-based wireless carrier Iusacell for $2.5 billion, which could lead to additional investments or acquisitions that weaken credit measures in the intermediate term. + We are revising our rating outlook on AT&T to negative from stable and affirming the 'A-' long-term corporate credit rating and the 'A-2' short-term rating. + The negative outlook reflects our expectation that leverage could rise to 3x or higher over the next few years. NEW YORK (Standard & Poor's) Nov. 10, 2014--Standard & Poor's Ratings Services today said it revised its ratings outlook on Dallas-based AT&T Inc. to negative from stable. At the same time, we affirmed the 'A-' corporate credit rating and 'A-2' short-term rating on the company. "The outlook revision to negative primarily reflects our expectation for slowing...