Tesla Motors chief Elon Musk said he would like to unveil a prototype sports utility vehicle (SUV) based on the all-electric Model S platform by the end of next year "if it's ready".

He was speaking after an event at which Tesla officially opened the car plant, formally known as New United Motor Manufacturing Inc (NUMMI), it bought for US$42m in May, where production of the Model S sedan is set to begin in 2012 at an eventual rate of up to 20,000 a year.

"There's many people that want to drive a sedan, and some people who want to drive an SUV," Musk told Reuters.

The 5.5m sq ft (510,000 sq m) factory, California's only remaining vehicle assembly plant, had a capacity of up to 500,000 cars per year and Tesla will use less than one-fifth of the space when production starts.

Of 500 initial employees, 70 are former NUMMI workers, and Tesla hopes to add 500 more workers in its ramp-up, Senator Dianne Feinstein said at the opening ceremony, which included the unveiling of a huge sign on the side of the dormant factory, easily visible from the busy motorway nearby.