Apple has shed new light on its top-secret driverless car project, as chief executive Tim Cook described the challenge of building autonomous vehicles as "the mother of all" artificial intelligence projects.
Mr Cook said Apple was ploughing resources into developing technology to control driverless vehicles, although he refused to rule out the Silicon Valley firm building its own car at some point. The Apple boss spoke as shares in his company and other US tech firms came under pressure amid concerns that a sector-wide boom is losing steam.
Mr Cook tried to restore faith in Apple's ability to strike out into new territory with his most detailed comments yet about a venture shrouded in secrecy.
"We're focusing on autonomous systems," said Mr Cook in an interview with Bloomberg TV. "Clearly one purpose of autonomous systems is self-driving cars. There are others. We sort of see it as the mother of all AI [artificial intelligence] projects." He added: "It's probably one of the most difficult AI projects actually to work on."
It was initially thought the company was going to challenge the automotive giants of Detroit, which are racing to build their own self-driving cars. But Apple's ambitions narrowed last year after Apple veteran Bob Mansfield was put in charge of the programme, dubbed Project Titan.
Google parent company Alphabet has also shifted the focus of its driverless technology for installation in cars built by established automotive firms.