Elon Musk throws down the gauntlet and challenges Mercedes to spend more than $1 billion on electric cars.

News broke last Thursday that Daimler, Mercedes' parent company, was investing $ 1 in its Alabama plant to start building an electric SUV in 2020.

Many outlets said the investment was an obvious challenge to Tesla, a formidable competitor in the US' electric space that plans to build its own compact SUV, the Model Y in 2020. Tesla CEO Elon Musk, however, begs to differ.

"That's not a lot of money for a giant like Daimler/Mercedes. Wish they'd do more. Off by a zero," Musk said on Sunday on Twitter.

Musk has long welcomed competition in the electric-vehicle space, saying it will help speed the growth of sustainable transportation. He open-sourced patents in 2014 as part of that aim.

Musk's comment supports his stance that automakers with a bigger cash cushion should do more to advance electric cars.

"It doesn't really harm Tesla but helps the industry," Must said during a 2014 call, "And I think actually it will help Tesla, mostly with respect to attracting and motivating the world's best technical talent."

Daimler responded to Musk's tweet, noting that it said in Nov. 2016 that it would spend $10 billion on next-generation electric vehicles and $1 billion on battery production.

Daimler has been cutting checks to help advance divisions that go after Tesla's core businesses, from home energy to electric vehicles.

In May, Mercedes parameter with vivnt solar to sell smart solar ecosystems to California residents, a challenge to Tesla's solar roof rollout its home turf.

Mercedes will also offers of electric version of all its models starting in 2022.

Daimler is shaping up to be Tesla's biggest competitor yet, but Musk's tweet indicates he isn't wary of the mounting challenge.

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