he said eight new Alfa models would be introduced from late 2015 through 2018.
"They've got to develop in the space of four years an entire portfolio of vehicles," AutoTrends analyst Joseph Phillippi said. "That's a huge engineering challenge."
While the U.S. luxury market is growing, the competition is fierce. Mirko Mikelic, senior portfolio manager for Clear Arc Capital, said it is hard to believe Alfa Romeo "will come in and start muscling out" rivals.
Among them are well-established brands such as Daimler's Mercedes-Benz and BMW, which are only making it tougher for competitors as they push down market to vehicles starting as low as $30,000, analysts and bankers say.
Alfa's planned North American return after leaving in 1996 was preceded by the re-introduction of Fiat in 2011. However, sales of the subcompact Fiat 500 have disappointed and Fiat dealers are struggling with only two models to sell. Fiat sales in the United States and Canada were about 51,000 last year.
In acknowledging that the company's overall plan for the 2014 to 2018 period is aggressive, Marchionne said he understood Wednesday's nearly 12 percent drop in the stock price. "We've had a phenomenal run in 2014 ... and I am not surprised that people took some money off the table," he said.
Marchionne also said he can "pull the plug" on the plan to invest 5 billion euros ($7 billion) to remake Alfa.
That did not make investors feel any better about an overall plan that includes the goal of boosting annual global sales by about 60 percent from 2013 to 7 million vehicles.
Fiat Chrysler also intends to boost its U.S. market share to 15.8 percent from 11.4 percent last year. That would position it for second place, and analysts and bankers say Ford Motor Co and Toyota Motor Corp will not let anyone pass them without a fight.
Even believers know they are taking a chance. "Whoever bets on Fiat today, bets on a possibility, on a potential," said Roberto Lottici, fund manager at Ifigest.