SAN FRANCISCO, Oct 21 (Reuters) - Tesla ​is aiming to start selling its Cybercab robotaxis to the public by the end of this year, its ‌engineering chief said on Wednesday, even as the US auto safety agency probes the vehicles that come without manual controls which federal regulations typically require.

The gold, two-seaters – that come with butterfly doors and drive themselves without any steering wheel, pedals or mirrors – are one of the key bets CEO Elon ​Musk has made in his ambition of turning the EV maker into an AI and robotics company.

"As Tesla grows, we'll ​mainly deliver fully designed autonomous vehicles to our customers and Cybercabs will be the first," Lars Moravy, ⁠Tesla's vice president of vehicle engineering, told analysts after reporting third-quarter results.

"We're trying to get Cybercabs to customers by the end ​of this year, 2026," he said. "As we start small this year, and we learn ... about delivery and ownership and fleet management of ​autonomous vehicles in customer hands, we'll continue to scale that."

After years of missed promises by Musk, Tesla started offering paid rides on a small fleet of Cybercabs in Austin, Texas, early last month amid a frenzy of fans and social media influencers.

Just hours later, the National Highway Traffic Safety Administration (NHTSA) said ​it opened an investigation into Cybercabs to assess how Tesla determined the cars comply with federal vehicle-safety regulations.

Those regulations, written decades ago for ​human-driven vehicles, require manual controls and limit commercial deployment of vehicles that are designed without them.

Unlike most other countries, where new vehicle models and ‌technology need ⁠regulatory clearance ahead of launch, automakers in the US can deploy them on the public roads by self-certifying that they meet federal standards.

NHTSA declined to comment. The agency last month said it was looking into the basis of Tesla's certification of the Cybercab and the extent to which the company determined that certain standards were not applicable to the vehicle. Tesla has until October 30 to ​respond to the agency.

NHTSA has proposed ​changes to federal safety standards ⁠to allow AVs that are designed without human controls. Until those changes are complete, existing standards remain in force, NHTSA has said.

SCALING THE CYBERCAB

"I think the key thing which we are trying ​to make sure is that we have all the regulatory approvals where we can start deploying ​the Cybercabs as ⁠fast as we can produce them," Ashok Elluswamy, Tesla's head of AI, said on the call.

That aside, "scaling would not be that much of a challenge," he said, adding that the Cybercab was "one of the easiest products" to scale in terms of manufacturing.

The Cybercab is part of ⁠Tesla's robotaxi ​network that includes autonomous Model Ys, some with human safety monitors. Over time, ​Tesla intends to make the Cybercab the main driverless vehicle model operating within a larger robotaxi network.

Tesla plans to expand the Cybercab service to Dallas next month, Elluswamy ​said.

The vehicle, however, will mainly be Tesla owned and used for its ride-hailing service, Musk said.