NEW YORK (AP) — Advertisers' growing wariness of the world economy suggests that global ad spending is going to grow less this year than previously thought.

In its latest report, ZenithOptimedia, a forecaster owned by the ad agency Publicis Groupe SA, says it expects ad spending to grow by 4.3 percent in 2012, to $502 billion. That's down from its March forecast of a 4.8 percent increase.

Financial turmoil in Greece and worries about the future of the euro have contributed to slowing economic growth across the world's richest countries. This is making advertisers more cautious.

But Zenith says major events, including the Euro 2012 Football Championship, the Olympics in London and the U.S. presidential election, will help, adding $6.3 billion to the global ad market.