Tesla's stock dropped more than 6% in after-hours trading Wednesday after the electric automaker said it might not be able to deliver as many cars as it had planned for this year. That's despite better-than-expected second quarter results.

Tesla recorded $1.2 billion in adjusted revenue, higher than the $1.19 billion Wall Street had expected. Its adjusted loss was at $61 million or 48 cents a share, lower than analysts' forecast of 59 cents.

In its earnings report, the company also said it was revising its full-year forecast for deliveries of the current Model S and the forthcoming Model X. From 55,000, the target is down to between 50,000 and 55,000.

"It was a surprise to us," Ben Kallo of Robert W. Baird & Co. told Bloomberg. "In the long run 5,000 cars is not a big deal, but it does raise eyebrows about the longer-term ramp."

The company attributes the estimate reduction to production and supplier complexities, especially with Model X, its first sports utility vehicle.

"The Model X is a particularly challenging car to build, maybe the hardest car to build in the world," Elon Musk, Tesla chief executive, said. "But it is an amazing vehicle and I think it will blow people away."

The biggest challenge is with the SUV's second-row seat, which Musk described as a sculptural work of art.

Issues with Model X could hamper Model S production, as both models are produced on the same general assembly line at Tesla's factory in Fremont, California.

The company also said a week-long delay due to a failure by some supplier to deliver sufficient parts could cut production by 800 vehicles.

But Musk said the first batch of Model X cars will be out by next month as promised.

Tesla has been making a lot of capital investments, causing its quarterly net loss based on generally accepted accounting principles to balloon to $184 million. That's almost triple from a year earlier.

Expenditures came from getting Tesla's Fremont factory ready for the production of Model X as well as building the world's largest battery factory east of Reno, Nevada.

It has also spent more on research and development for such projects as the highway autopilot system. Musk said this feature, which automatically controls steering and acceleration, may be released to certain drivers in 10 days. Wide release is at least a month after that.

Tesla is likewise expanding its network of Supercharger stations, opening a new station every day. Right now, the company has 487 Supercharging stations globally.

This quarter, Tesla will start producing battery packs for homes.

The company is also developing a more affordable sedan called Model 3, although it is not due out until 2017.  

Once it is able to produce huge numbers of vehicles, Tesla will set up factories in other markets, including Asia and Europe.

Currently, the carmaker based in Palo Alto, California has one retail store in China, the world's largest auto market. It will soon build five more there.