SAN FRANCISCO - The leader of Uber's self-driving car program says the ride-hailing service he launched this week in San Francisco will continue despite regulators' objections.

California transportation officials have demanded that Uber stop picking up passengers in a handful of Volvo SUVs tricked out with a suite of sensors that let the cars steer, brake and accelerate.

Uber's Anthony Levandowski told reporters Friday that he disagrees with the state's demand to suspend operations until it gets a special permit because the cars aren't subject to California's self-driving regulations.

Levandowski says Uber doesn't need a permit because a backup driver is behind the wheel monitoring the car. He says that means the Volvos aren't "autonomous vehicles" under state law.

The state has threatened legal action. Officials didn't immediately respond to requests for comment.