Fiat shares have dropped 10 percent as investors expressed skepticism over a new business plan to launch Fiat Chrysler Automobiles as a leading global player.

Analysts said Wednesday that an ambitious plan to invest 48 billion euros ($67 billion) to boost volumes to 7 million by 2018 from 4.4 million last year failed to adequately address the financing requirements. The plan does not include a capital increase.

CEO Sergio Marchionne emphasized that cash-generating Ferrari was not for sale — a topic of frequent market speculation — and that an initial public offering was not imminent.

Bernstein analyst Max Warburton said Fiat's first-quarter results, which showed losses widening, "provided a sobering reminder of the fragile foundations on which FCA must build its ambitious plans."

Mediobanca called the plan "challenging but achievable."