TECH giants Apple and Google "can do more and know more" about self-driving cars than was previously thought, a senior car executive has said.

Speaking to German paper Welt am Sonntag, Dieter Zetsche, the chief executive of car company Daimler and head of Mercedes-Benz, said that Google and Apple are much further along with autonomous vehicle technology that has been speculated.

Zetsche got an insight into how Silicon Valley is getting into the car industry on a recent business trip to California, during which he tried to discover the factors behind the area's "creative spirit."

Although both companies were more advanced than Zetsche thought, he also said: "At the same time they have more respect for our achievements than we thought."

This is high praise coming from the Daimler CEO, whose company last year unveiled a prototype self-driving 18-wheeler lorry, the first vehicle of its kind licensed for road tests.

Mercedes have also created a prototype self-driving car, the F015, one of the sleeker-looking and more futuristic concepts.

Apple and Google have aggressively recruited experts and engineers from traditional car companies over the last few years, and although no solid details on what they are working on have been announced, it is understood that both companies are committed to one day releasing self-driving vehicles to the public.