IS IT A SWOOPY-LOOKING sedan or a four-door coupe? Both, says Mercedes-Benz, of its CLS that lives a double life as a roomy and versatile rival to traditional upmarket two-door coupes like the BMW 6 Series and Jaguar XK.

Based on the same rear-wheel-drive platform as the strong-selling E-Class, the CLS makes its public debut in production guise at the Geneva motor show, prior to heading Stateside a bit more than a year from now.

Differing little from the earlier CLS concept car shown at last year's Frankfurt show, the production version of the CLS receives a toned-down grille, door handles, mirror housings and aluminum wheels. The concept car's panoramic glass roof is also gone, though as on the E-Class it is likely to be offered as an option.

Bucking the recent coupe trend toward rear-hinged doors, the CLS's long rear doors open in the conventional manner, hinging at the front on a strengthened side member. The B-pillar is retained, though clever styling tricks, with darkened paneling on the pillars and tight shut-lines between the doors, give it an almost pillarless appearance.

Stuttgart's new sedan-***-coupe is longer, wider and lower than the E-Class, but because it rides on the same wheelbase, the front and rear overhangs are extended, most notably at the rear.

Inside, Mercedes-Benz's designers have given the CLS a unique-looking dashboard swathed in wood and boasting familiar E-Class switchgear. Rear-seat passengers benefit from ease of entry and ample space typical of luxury sedans.

CLS will be available in the United States in early 2005, with the company's new 24-valve 272-hp 3.5-liter V6 in the CLS350, and the familiar three-valve-per-cylinder 24-valve 306-hp 5.0-liter V8 in the CLS500. About 18 months after CLS goes on sale, two new 32-valve V8 engines will join the lineup: a 350-hp 4.6-liter and a 400-hp 5.5-liter. When they arrive, the existing 5.0-liter V8 will be phased out of production. But before the new V8 engines arrive, Mercedes plans to launch a CLS55 AMG model. Due to premier at the Paris motor show in September, it gets the supercharged 500-hp 5.5-liter V8 engine used in a variety of AMG models.

Need more? In preparation for the new AMG-developed 6.3-liter V8 engine in 2006, Mercedes also has registered the CLS63 name, which AutoWeek sources say will replace the CLS55.