Tesla shares topped $1,000 for the first time on June 10, as reports surfaced that the company is pushing to ramp up production of its electric heavy-duty Semi truck.

According to Reuters, Tesla chief Elon Musk told his staff in an email Tuesday before the market opened that it was time to “go all out” to bring the Tesla Semi commercial truck to “volume production,” but he didn’t specify a time frame.

Just a month and a half ago, Musk said in an earnings call that the long-awaited battery-electric truck wouldn’t be in production until 2021.

Tesla’s shares rose about 6% to hit $1,000 on Wednesday after Reuters reported Musk’s email. Reuters noted that Musk’s message coincided with a surge in the share price of rival electric-truck maker Nikola. Nikola on Wednesday announced it had hired former Tesla executive Mark Duchesne to head its manufacturing and former Caterpillar exec Pablo Koziner to head its hydrogen fueling and battery recharging business.

Apparently in response to the latest news about the Semi, Nikola founder Trevor Milton tweeted, “I love the competition!” and touted the Nikola fuel-cell truck’s lighter weight.

I love the competition! Tesla's call to mass produce a semi is a good thing to Nikola's business model no matter what. I hear the their semi truck weighs 27,000 - 30,000 lbs for long range mile version. Our fuel cell should be 10,000 lbs less.

— Trevor Milton (@nikolatrevor) June 10, 2020

The two companies also appear to be in a battle as to who will have a zero-emissions pickup on the market first, the Tesla CyberTruck or the Nikola Badger. Nikola recently announced it is opening up reservations for the Badger on June 29.

We open up reservations for the most bad ass zero emission truck on June 29th. See the @nikolamotor Badger in person at #nikolaworld2020 this year. You'll get to see a real operating truck, not a fake show truck. Expect stamped metal panels, functioning interior w/ hvac, 4x4, etc pic.twitter.com/SkY9zV0bbs

— Trevor Milton (@nikolatrevor) June 8, 2020

“This is Elon making noise because of Nikola,” Ben Kallo, an analyst at Robert W. Baird, told Bloomberg. He said other factors are fueling the Tesla stock’s gain, including strong sales in China and the anticipation of a "Battery Day" event.

Initially, when the Tesla Semi was introduced in 2017, Musk announced production would begin in 2019. Companies such as Anheuser-Busch, J.B. Hunt, Fedex and UPS put in orders. Over the next year, Tesla Semis were spotted along highways and details started to emerge on an electric truck charging network. Then, in April 2019, during Tesla’s first-quarter earnings call, company officials indicated that production would begin in 2020. This was pushed back further in January, when a leaked email sent by Tesla to a company that had reserved one of the Semis reportedly said production would begin in the second half of 2020, with a limited run.