CANNES, France (Dow Jones)--GroupM, a unit of ad giant WPP PLC (WPP.LN) Thursday raised its forecast for this year's global advertising spending in another sign that the ad world continues its recovery. GroupM said it now expects global ad spend to rise 3.5% to $451 billion, compared to the 1% rise it predicted six months ago, driven mainly by emerging markets such as Brazil, Russia, India, Indonesia and China, as well as digital advertising. "China remains the world's biggest contributor to ad growth in 2010, accounting for one in three of all net new ad dollars we expect this year, and one in five as the rest of the world catches up in 2011," said Adam Smith, GroupM futures director. For 2011, the forecaster said it predicts ad spending to rise 4.5%. U.S. ad spending is expected to decline 1.3% to $145 billion this year. This is an improvement on last year though, when ad spending in the U.S. dropped 7%. In 2011, U.S. ad spending is projected to rise 2.5% to $149 billion, GroupM said. "The U.S media marketplace has clearly bottomed out earlier this year and we expect moderate growth in 2011 consistent with GDP improvement," GroupM Chief Investment Officer Rino Scanzoni said in a statement. "Television and on-line spending will outpace other media as they lead with return-on-investment metrics." GroupM's raised forecast is the latest in a recent series of positive signs in the ad world. ZenithOptimedia, a unit of Publicis Groupe SA (PUB.FR) in April raised its forecast for global ad spend to 2.2% from 0.9%. -By Ruth Bender, Dow Jones Newswires, +33 1 40171754; [email protected] (END) Dow Jones Newswires June 24, 2010 10:39 ET (14:39 GMT)