WPP has lowered its full-year outlook after not doing as well as expected from the Olympics, the US presidential campaign and the European soccer championships.
The company is the world's largest advertising group.
It said today that it expected revenue growth between 2.5-3% for the year, down from the 3.5% target it set in August. Third quarter revenue was up 1.6% to £2.5 billion sterling.
The company did not disclose profit figures in the trading update.
WPP said the three big events did support growth but not as much as expected, with money often switched from existing budgets, "particularly in the cases of the UEFA Championships and Olympics."
Revenue fell by 0.4% in North America and 2.1% in western continental Europe, WPP said. Latin America was the best-performing region with growth of nearly 15%.
WPP said that in the US it was worried about the government's handling of debt and the looming "fiscal cliff" of expiring tax and spending legislation, which could result in automatic tax increases at the end of the year if politicians do not agree on new budget terms.
"Fears remain that whoever wins the presidential election, will be unable to deal with these issues given a dead-locked Congress," the company said.