Investors are worried that Tesla CEO Elon Musk isn't spending enough time on the company as it rapidly ramps up production of electric cars, after committing to buy Twitter.

The company delivered 343,000 cars in the quarter - a record that was up more than 40% from the same period last year. However, it produced more cars than were sold, raising fears that demand may be slowing, as rising prices, higher borrowing costs and a major economic slowdown in the key China market discourage buyers.

Mr Musk conceded there was weakness in China but beat back suggestions that demand was cooling. He said the company expects to sell every car it makes. Deliveries of its own much anticipated electric truck are due to start in December, the firm said.

The company reported $3.3bn in profit, up significantly from a year ago. But questions about Tesla's growth path, as well as billions of dollars in stock sales by Mr Musk as he prepares a $44bn takeover of Twitter, have weighed on the company's shares in recent months.

Tesla dominates the electric vehicle market in the US, but it faces far more competition in Europe and China, where such cars are more popular. In the US, rivals have also been ramping up their efforts. German carmaker BMW said on Wednesday that it would spend $1.7bn to expand its electric vehicle production in the US.