// 16:32 UTC Elon Musk says supply chain disruption in China held up delivery of a key component for Tesla's "Optimus" robot, with authorities reportedly demanding an export license and guarantees about military applications. During an earnings call following Tesla's lackluster calendar Q1 results in which revenue slumped 20 percent to $12.925 billion and net income plunged 70 percent year-on-year to $420 million, Musk talked of difficulties in obtaining rare earth magnets used in robot motors. "We're working through that with China," he said. "Hopefully, we'll get a license to use the rare earth magnets. China wants assurances that these are not used for military purposes, which obviously they're not. They're just going into a humanoid robot. So that's not a weapon system." "There's not like an existing supply chain for the motors, gearboxes, electronics, actuators, really anything in the Optimus apart from the AI4, the Tesla AI computer, which is the same as the one in the car. "So when you have a new complex manufactured product, it will move as fast as the slowest and least lucky component in the entire thing. And for approximation, there's like 10,000 unique things." The billionaire, who previously predicted that a Tesla car would be able to make a driverless trip from Los Angeles to New York, said on the call: "Anyone you tells you they can predict with precision, the production ramp of the truly new product – doesn't know what they're talking about."