Rolls-Royce expects its new convertible, which will be based on the Phantom sedan, to account for up to 40 percent of the company's annual production.
The company built 703 vehicles in the first 10 months of 2004 and has said it wants to produce about 1,000 a year.
The convertible will debut in 2007, said Stefan Krause, chief financial officer of parent company BMW and temporary CEO of Rolls-Royce.
Krause sees Rolls-Royce adding more vehicles. "We want to further expand the range," he said in an interview. "It traditionally had allowed for some level of expansion. I am very comfortable with that part of the business being a contributor to the bottom line."
Rolls-Royce is considering longer-wheelbase and armored versions of the Phantom.
The convertible will be smaller than the 5660mm 100EX show car that appeared at the Geneva auto show in March, Krause said.
"The 100EX gives you a good idea of what kind of direction the car will take," he said.
BMW decided to give the convertible the green light because of enthusiasm for the 100EX concept, Krause said.
The convertible will use the Phantom's 6.75-liter V-12 engine. It will be built in Goodwood, England, where the Phantom is produced.
A Rolls-Royce spokesman said the convertible will cost more than the Phantom. The Phantom's base price in Europe is E216,950.
Krause took over Rolls-Royce last month when CEO Karl-Heinz Kalbfell left to head Alfa Romeo. Krause said he couldn't predict how long he'll be at the helm of Rolls-Royce while the company searches for a new CEO.