Ford, General Motors, Stellantis, and the United Auto Workers union will attend a White House event Thursday in support of vehicles that use clean energy.

But the story may be who won't be attending the event: electric car giant Tesla.

“There is one car manufacturer that seems conspicuously absent from this event today and that is Tesla. I’m curious why,” Andrew Ross Sorkin, co-anchor of CNBC program "Squawk Box" asked Transporation Secretary Pete Buttigieg on Thursday.

“I’m not sure,” Buttigieg responded.

The oversight of Tesla wasn't lost on outspoken CEO Elon Musk. The billionaire tech leader posted a comment on Twitter that touched on Tesla's absence.

CNBC showed the tweet on the screen. Sorkin followed up by asking Buttigieg if he saw the tweet.

"I haven't seen that," Buttigieg said.

Buttigieg did not reference Musk or Tesla. Instead, he pivoted to the overall electric car industry.

"We're excited about all of the momentum for making sure that Americans can drive electric vehicles going into the future," Buttigieg said.

"By the way, we're also moving toward a future where this is all across the market. I don't want there to be a perception that this is just kind of a luxury thing."

Biden will sign an executive order that will set a national zero-emissions goal to make half of all new cars and trucks electric by 2030.

“You have newer companies and legacy companies that are both saying we have to move in this direction,” said Buttigieg.

CNBC asked a White House official about Tesla’s absence, the response was similar to Buttigieg’s which explained all-electric car companies will be supported in the transition.

“We of course welcome the efforts of all automakers who recognize the potential of an electric future and support efforts that will help reach President Biden’s goal, and we’re excited to see the support and goals not just from the three automakers who will be here today, but all automakers who realize this potential,” the official said.