Shares of Tesla (TSLA.O) jumped nearly three per cent on Thursday after Chief Executive Elon Musk said the electric car company expects to unveil its planned commercial truck in September.

Musk last year announced plans for electric vehicles ranging from a commercial truck called the Tesla Semi to a public transport bus, a "new kind of pickup truck" and a compact sport utility vehicle.

"Tesla Semi truck unveil set for September. Team has done an amazing job. Seriously next level," Musk said in a tweet on Thursday.

"Pickup truck unveil in 18 to 24 months," he added in another Tweet.

Tesla's stock was up US$8.14, or 2.74 per cent, at US$304.98 after Musk's tweets.

Shares of Tesla have surged 41 percent to record highs this year, and this week the Silicon Valley company briefly became the largest U.S. car maker by market capitalization, beating out General Motors Co (GM.N).

Proponents believe Tesla's stock rally and high valuation are justified based on long-term expectations for growth.

Skeptics and short sellers say Tesla's growth targets are unrealistic and that the company risks being overtaken by GM, Ford Motor Co (F.N) and other deep-pocketed manufacturers ramping up their own electric-vehicle offerings.

The Palo Alto, California company, which is not profitable, is rushing to launch its mass-market Model 3 sedan in the second half of 2017 and quickly ramp up its factory to reach a production target of 500,000 cars per year in 2018. By comparison, GM sold 10 million cars and Ford sold 6.7 million.