Tesla Motors Inc., the electric-car maker led by Elon Musk, won’t decide until year end where to build a battery “gigafactory” even as it readies multiple plant sites, the billionaire clarified for investors.

The company first proposed the sprawling battery plant — which Tucson is vying for — in February to supply lower-cost lithium-ion cells for its cars and packs for home-power storage devices. Tesla will soon start preparation in as many as three states “all the way to creating a foundation,” completing plans and gaining local approval, Musk, 42, said Tuesday at Tesla’s annual shareholder meeting in Mountain View, California.

“It might actually be three states that we do it in,” he said. “I would expect that we do a down-select for gigafactory 1 before the end of the year.”

Tesla plans to boost deliveries of its Model S sedan that’s priced from about $71,000 by more than 56 percent this year as sales to China and other international markets expand. Musk has said the Palo Alto, California-based company’s goal of selling lower-priced electric cars within the next three years depends on opening its gigafactory by 2017.

Plans for the plant are “quite advanced” and discussions with Panasonic Corp. (6752), Tesla’s main supplier of battery cells, about its involvement in the project take place daily, Musk said. The proposed plant would eventually cost as much as $5 billion to build and employ as many as 6,500 people, Tesla has said.

The company is studying sites in Arizona, New Mexico, Nevada and Texas. Musk last month said California is also a potential candidate for the factory.