In a seeming turnaround from comments he made just earlier this week, Fiat/Chrysler CEO Sergio Marchionne revealed that the Alfa Romeo brand will finally make its long-anticipated return to the U.S. by year-end, launching with the new 4C sports car.

The executive also revealed that Fiat has signed a deal with Mazda that will have them produce a 2-seat new sports car at the Japanese maker’s plant starting in 2015. It will serve as an addition to Alfa’s line-up and a replacement for the aging Mazda Miata.

“We’re finalizing the car now,” CEO Marchionne said of the new Alfa 4C, “so it should be here (in the U.S.) by the end of the year.”

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The news is likely to resonate well in some circles. Alfa Romeo was once one of the most popular Italian brand sold in this country but it abandoned the U.S. market two decades ago due to a variety of problems, including poor quality. It has since tried a number of times to return but until now, such efforts have failed to gain traction.

Marchionne made the revival of the Alfa brand one of his key points during a day-long conference in November 2009 outlining his plans to turn things around at Chrysler, which had just emerged from bankruptcy until the control of Alfa’s parent, Fiat SpA.

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But while most of the turnaround plan has gone according to plan, Alfa’s return has fallen behind schedule, and during a media roundtable held during the North American International Auto Show on Monday, Marchionne appeared to be signaling yet another delay. He cautioned that work on the small 4C sports car was not yet meeting his approval and that he wasn’t ready to sign off on its debut in the U.S. as the first new American Alfa model.

“This undertaking to bring Alfa back is a one-shot deal,” he cautioned. “We are not going to do this twice.”

Of particular concern, he hinted, was the powertrain, which he stressed had to have the right feel and even the right sound long associated with Alfas past. In the sort of blunt, often politically incorrect comment Marchionne has become known for, he declared it had to be a “Wop” engine, a typically negative reference to something or someone of Italian descent.

But even after cautioning reporters, Marchionne concluded, “Alfa Romeo is coming. There is not a single doubt.”

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What has happened over the last four days to permit the hands-on executive to announce a relatively specific timetable for that return is unclear. But in his comments today at an industry breakfast, Marchionne did note that work on the Alfa 4C powertrain is not finalized while the choice of the basic vehicle architecture and the models to come to the U.S. have apparently been locked in place.

The 4C is the sports car Fiat is counting on most as it struggles to revive the once vibrant Alfa, but it is only one of nine models the maker has confirmed it plans to launch by 2016. Alfa, Marchionne has explained, will be one of a select group of Fiat and Chrysler brands, a list also including Jeep – that the trans-Atlantic alliance will take global in the coming years.

Most of those products will be assembled in Italy but the maker now plans to produce a small, rear-drive sports car in Japan. It will be the result of a joint development effort with Mazda, and it will be produced at one of that maker’s Japanese plants.

The project is similar to one that teamed up Toyota and Subaru, the former maker marketing the sports coupe in the U.S. as the Scion FR-S, Subaru bringing its version here under the BR-Z nameplate. As part of the new joint venture the Mazda sports car will replace the aging Miata. There’s no word on what Alfa will call its model.

It’s clear that Marchionne is hoping the news about Alfa will finally end speculation about the struggling brand’s future.

In recent months, senior officials with German rival Volkswagen AG have repeatedly suggested Fiat should sell them Alfa. Marchionne has repeatedly insisted Alfa Romeo is not for sale, and on Monday frustratedly told reporters, “I’ve got to come up with a German version of ‘No.’” I think it’s called ‘Nein.’”