March 8 (Reuters) - Rivian jumped 7% on Friday as its cheaper R2 SUV racked up tens of thousands of reservations within hours of its launch, fueling optimism that the electric-vehicle maker could expand in the mass-market segment.

Unveiled on Thursday, the smaller R2 SUV, which will start at $45,000, has attracted more than 68,000 reservations, CEO RJ Scaringe said in a post on X.

"Given Tesla has shown little ambition to move into the SUV space, Rivian could be one of the few EV SUVs on the market that most investors will likely want to buy over the next 3-4 years," Evercore ISI analyst Chris McNally said in a note.

Rivian plans to start producing the R2 at its existing U.S. factory to hasten deliveries in the first half of 2026.

In a surprise move, the company also introduced the R3 and a more powerful R3X variant on Thursday. The R3 will be cheaper than the R2 and will be launched after that vehicle.

The launches come when EV demand is rising at a slower pace than automakers expected, forcing market leader Tesla to slash prices to spur sales of its aging model lineup.

(Reporting by Akash Sriram in Bengaluru; Editing by Sriraj Kalluvila)