Tesla Motors Inc. plans to boost production of electric cars to "at least a few million a year" by 2025 from fewer than 40,000 last year, Chief Executive Officer Elon Musk said Tuesday.

Speaking at an industry conference in Detroit, Musk said Tesla may not be profitable until 2020. In addition, Tesla's sales in China were unexpectedly weak in the fourth quarter. He blamed a misperception by city-dwelling Chinese consumers that they might have difficulty charging their electric cars.

"We'll fix the China issue and be in pretty good shape probably in the middle of the year," he said.