SAN FRANCISCO, March 19 (Reuters) - Uber will invest ‌up to $1.25 billion in electric vehicle maker Rivian as part of a deal in which the ride-hailing firm will start deploying 10,000 fully autonomous R2 SUVs as robotaxis from 2028, the companies ​said on Thursday.

Rivian's shares rose about 9% in premarket trading.

San Francisco-based Uber will ​make an initial investment of $300 million, and will fund the remaining ⁠amount through 2031, subject to Rivian meeting certain autonomous milestones, the companies said.

Interest in ​driverless taxis has surged in recent months after years of missed promises, with artificial ​intelligence and tech partnerships offering hopes of solving complex traffic scenarios faster and mitigating high costs.

While Rivian, known for its high-end R1S SUVs and R1T pickup trucks, has not launched a robotaxi yet, ​it unveiled its first custom computer chip for self-driving in December. The company is ​also gearing up to roll out its smaller, more affordable R2 SUVs this quarter.

Meanwhile, Alphabet's Waymo, which ‌runs ⁠about 2,500 robotaxis in several U.S. cities, has accelerated its rollouts, while Tesla has launched a small robotaxi service in Austin, Texas, with CEO Elon Musk promising rapid expansion this year.

R2 robotaxis will be available exclusively on Uber's platform, starting with San Francisco and ​Miami, the companies said, ​adding that Uber ⁠has the option to buy up to 40,000 more beginning in 2030.

"Should all milestones be achieved, the companies will have deployed ​thousands of unsupervised Rivian R2 robotaxis across 25 cities in the ​U.S., Canada, ⁠and Europe by the end of 2031," they said.

Uber is positioning itself as a marketplace for multiple robotaxi operators, and has partnered across much of the autonomous vehicle industry, including ⁠with Waymo, ​Baidu and Lucid.

It is also working with Nvidia on autonomous ​driving, leveraging the chip designer's AI and simulation platforms to support the development and scaling of robotaxi systems.