DETROIT (CNNMoney) -- Sergio Marchionne, CEO of both Fiat and Chrysler Group, said that while he's pleased with the re-launch of the Fiat brand in North America last year, he was "incredibly naive" to think he'd sell 50,000 of the tiny cars in the U.S. in 2011.
The company sold only 19,769 Fiat 500's in the U.S. last year. But Marchionne said the huge miss of the sales target was not a problem.
He said he chose the original sales target hoping to beat the 45,644 cars sold of the popular Mini Cooper, sold in 2010.
"It was a number that we said would be in excess of what Mini was selling in the United States. It was that simple," he said about the target.
Plans to introduce other cars to the line by 2013 and to expand the dealer network remain on track, he said.
"Let's be honest, we sold 2,009,000 cars in 2011," he said about Chrysler Group's global sales. In the grand scheme of things, he said the missed sales target for the Fiat 500 "is a rounding error."
"We set ourselves up for a fall," he said about the miss. "The future of Fiat is exactly the same as when we launched it."
He said the 2012 target for the 500 is between 25,000 and 35,000 in the United States and another 5,000 in Canada. Overall, the target for Chrysler Group's global sales is 2.4 million. (Chrysler brings back Dodge Dart)
He said the Mexican plant making the Fiat 500 for the North American market can continue to operate profitably by exporting the vehicles it makes to other markets, such as South America and China. The plant has a capacity of about 100,000 vehicles.
Fiat rescued Chrysler Group out of bankruptcy in 2009 with the help of a federal bailout that kept the automaker alive. Fiat has contributed technology, including more fuel efficient engines and models to Chrysler, helping it to revamp its lineup.
But when asked at a press conference at the Detroit auto show Monday if it was now fair to say that Fiat today needs Chrysler as much as Chrysler needs Fiat, he responded "Without a shadow of a doubt. I don't understand one without the other anymore."
Marchionne, 59, also said he's committed to staying as CEO of both automakers at least until their merger is completed in 2015.
"Succession is not on the table until after 2015," he said. But he wouldn't predict how far past the completion of the merger he'll stay, saying he will have been in the top job at Fiat for 12 years at that point.
He said he expects his successor will come from inside the combined automaker.
"We need to be able to select from the bench the guy who is going to come next, or the woman for that matter," he said.
He also said the decision on where to base the headquarters of the combined automaker will come no earlier than 2013 and no later than 2015. But he dismissed the question of whether the company will be based in the Detroit area or Italy or some other location as relatively unimportant.
"We're a bunch of traveling salesmen," he said. "It doesn't really matter." 
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