"We will be manufacturing a fourth model here from next year onwards," said Eckhard Cordes, head of the Mercedes Car Group.
Company executives say that the model is the successor to the G class and will be called the GL. Its project name is X164.
The other three models built at the plant are the M class SUV and the long and short variants of the new R-class sport wagon.
Mercedes sold about 6,400 units of the 26-year-old G class in 2004. The classic SUV will continue to be built at Magna Steyr in Graz, Austria, until at least until 2007 because "we still have a few army orders to deal with," said Cordes.
The G-class successor, which like the R class is based on the M-class design, will be longer than the S class sedan with a length of 204 inches and have a third row of seats.
The new G class will debut at the Detroit auto show next January and its market launch will be mid 2006. The basic price will be around 56,000 euros, or about $72,000 at current exchange rates.
Mercedes doubled the capacity at the plant to 160,000 units for the launch of the R class. The number of employees will be increased from 2,000 to 4,000 by the end of this year.