Tesla is set to unveil its semi truck in September, according to a tweet from CEO Elon Musk on Thursday.

He also said a pickup truck will be unveiled in the next 18 to 24 months.

Elon

Elon

Tesla was not immediately available for additional comment. But the automaker has long planned to add both a semi truck and a pickup truck to its lineup of cars. Musk discussed both in the second volume of his "master plan" for Tesla.

"We believe the Tesla Semi will deliver a substantial reduction in the cost of cargo transport, while increasing safety and making it really fun to operate," Musk wrote in his plan.

Responding to questions on Twitter Thursday, the CEO also offered details on two more of the company's future models.

He said Tesla's next generation Roadster will be a convertible. The Roadster was the first car Tesla produced, from 2008 to 2012.

Elon

Musk also said the final Model 3 will be unveiled in July.

Elon

Tesla's stock was roughly 3 percent higher in late trading, near $307 a share.

The stock has hit all-time highs in recent days, putting its market value above far larger automakers.

for the latest on the markets.