For North America in the third quarter, organic revenue for the holding company -- which buys media for GM via Starcom MediaVest Group -- dropped 5.3%. By comparison, if GM's results were stripped out, the decline would be 2.3%.

On a conference call to discuss 3Q results, CEO Maurice Levy said Publicis expects organic revenue to continue to drop in the fourth quarter, due to GM curtailing spending.

But he expressed optimism results could improve if some of GM's new launches -- such as Buick models, for which agency Leo Burnett has worked on creative -- sell well. That could persuade GM to increase Buick investments.

Levy told investors on the call that GM is making payments "regularly" to Publicis. "It's important to point [that] out because there has been some concern within the credit agencies and [by] some analysts," he said.

Going forward, Levy declined to comment on discussions held with GM about the automaker's plans in 2010, but said: "We are cautiously optimistic."

"It will take time before GM is in a recovery mode," he said.

Publicis' total revenue for North America in 3Q increased by 1% to $722 million. That was in contrast to declines in Europe, Asia-Pacific and Latin America.

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