SAN FRANCISCO (Reuters) -Uber ( UBER ) will invest $300 million in electric vehicle maker Lucid in a robotaxi deal that aims to start with one major U.S. city late next year, the companies said on Thursday.

Shares of Lucid surged more than 56% to $3.58 in trading before the bell after the company also said it had proposed a one-for-ten reverse stock split of its class A common stock.

Over six years starting in 2026, Uber ( UBER ) will acquire and deploy over 20,000 Lucid Gravity SUVs that will be equipped with autonomous vehicle (AV) technology from startup Nuro, the three companies said in a statement.

The agreement illustrates the renewed plans and push for financing for self-driving cabs years after a first wave of autonomous driving investment produced only a limited number of vehicles. Tesla has recently launched a robotaxi trial in Austin and Alphabet's driverless taxi unit Waymo is speeding up its expansion.

As part of their announced deal, Uber ( UBER ) will invest hundreds of millions of dollars in Lucid and Nuro, which supplies self-driving technology to automakers, the joint statement said. Of that, $300 million will go to Lucid, the EV maker said in a separate filing to the U.S. Securities and Exchange Commission on Thursday.

Uber's ( UBER ) latest move underscores its renewed push into the robotaxi space after exiting in 2020. Since then, Uber ( UBER ) has pivoted to partnerships with several technology developers, including Waymo and Aurora.

The deal with Lucid follows Uber's ( UBER ) robotaxi agreement in April with Volkswagen that will supply its ID.Buzz vans for commercial service planned for Los Angeles next year.

But commercializing AV tech has been much harder than anticipated with high costs, tight regulations and federal investigations forcing many, including General Motors' Cruise, to shut down. 

Some still in the race include Amazon.com's Zoox, which is testing a robotaxi without manual controls and plans to launch commercial services in Las Vegas this year.

After years of missed promises, Tesla started a restricted trial with about a dozen of its Model Y SUVs in Austin, Texas, last month. CEO Elon Musk has said it will expand the service rapidly to other U.S. cities this year.

Waymo has been growing cautiously for years and operates in several U.S. cities with about 1,500 vehicles. It crossed 100 million miles of autonomous driving this month. 

A prototype of the Lucid-Nuro robotaxi is already operating autonomously on a closed circuit at Nuro's testing facility in Las Vegas, the companies said. 

"We are expanding beyond our traditional EV technology leadership and working on partnerships and going now into areas that in the past we have not really focused on," Lucid's interim CEO Marc Winterhoff told Reuters.

Nuro, co-founded and led by former Waymo engineers, has expanded from making last-mile delivery vehicles to providing its self-driving technology for commercial and passenger vehicles.

"We have other very active conversations going on the personal vehicle side ... where we would integrate Nuro driver into vehicles that will get sold to end consumers," Dave Ferguson, Nuro's co-founder and president, said. 

Nuro will still need to apply for state-level operating licenses though it holds some licenses from their previous delivery operations, he said.