Two Italian icons come together as Fiat launches the latest version of its minicar, the 500 Gucci edition.

Fiat’s latest version of the little 500 minicar will make its debut on the runway rather than the auto show stage, the high-style Gucci edition debuting on September 8^th during New York’s annual Fashion Week, a week ahead of the annual Frankfurt Motor Show where many of the maker’s other new product will be unveiled.

Attracting fashionistas will be critical for the Italian automaker which is in the midst of its re-launch in a U.S. market it had abandoned two decades earlier.  But despite the upcoming introduction of yet another version of the Fiat 500, investors are growing concerned that the maker’s American revival isn’t going as well as planned.

Fiat shares fell by as much as 6% in Italy on Tuesday, reflecting mounting concerns about the sales shortfall for the 500 in the States.  Through the end of July, American motorists had purchased just 11,500 of the cars, making it increasingly unlikely Fiat can hit its 50,000 target for 2011.

Launched earlier this year in coupe form, Fiat revealed the convertible version of the minicar at the April New York Auto Show and will shortly add the Fiat 500 by Gucci, the most stylish – but also the most expensive version of the 4-seater yet.

“With Gucci as our design partner, we’ve amplified the Italian style of our Fiat 500 with unique exterior and interior looks that will make the car truly unique on the road,” said Laura Soave, Fiat’s North American brand director.

The executive has acknowledged that the 500 launch is going slower than expected but also defended the company by cautioning the addition of new Fiat dealers is also running behind schedule.  With more now coming online, she insists “We have coverage now, so now is the time for us to turn this up.”

U.S. prices for the Fiat 500 by Gucci have not yet been announced, though in Europe the convertible version is to carry a sticker of as much as 20,000 Euros – or nearly $29,000 – which would be several thousand more than the standard cabriolet version.  The base version of the Fiat 500 coupe starts at $15,500 in the States.

The glossy black special edition features the green-and-red signature Gucci stripe along the body side, the seatbelts and seat back.  The brand’s interlocking GG logo is also displayed in prominent places on headrest and wheels.  The interior is done up in leather with bold white accents.

The idea of linking two of Italy’s iconic brands was conceived by Lapo Elkann, scion of Fiat’s founding Agnelli family, who brought the idea to Gucci Creative Director Frida Giannini over lunch.

The launch of the Fiat 500 coincides with the Italian maker’s increased role in the management of American automaker Chrysler.  Fiat was given a 20% stake in the U.S. company in 2009, following Chrysler’s emergence from bankruptcy.  It has since increased that to 53.5% and Fiat/Chrysler Chairman Sergio Marchionne eventually hopes to boost that to 70% or more.

The two makers have increasingly moved to share products, the big Chrysler 300 sedan now sold in Europe as the Lancia Thema, for example, while new Fiat models will eventually replace the smaller Chrysler 200.  But Marchionne decided the 500, a European icon, would be used to revive the Fiat brand in the States.  The company had pulled out of the markets decades earlier due to ongoing quality problems and steadily declining sales.