SAN FRANCISCO, Jan 5 (Reuters) - Vietnamese car maker VinFast plans to build electric vehicle battery cells and packs in its planned U.S. manufacturing complex, its global chief executive told Reuters on Wednesday. VinFast, part of Vingroup JSC (VIC.HM), the largest conglomerate in the Communist-ruled country, had previously said it planned to start producing electric vehicles in the United States in the second half of 2024. VinFast is betting on the U.S. market, where it plans to debut affordable electric sport utility vehicles late this year with its battery leasing models. "We will build our gigafactory in the U.S. as well," said Le Thi Thu Thuy, Vingroup vice chair and VinFast Global CEO. The company will continue to source batteries from its suppliers, she added. It will initially assemble battery packs with cells sourced from its supplier at its U.S. complex before starting its own production there, she said. "We have narrowed down from I think, over 50 sites to about three sites," she said during her U.S. visit to attend the Consumer Electronics Show in Las Vegas. She will visit some sites during her trip before making a decision this year, adding that the "mega site" would also include an electric bus factory. In December, Vingroup said it had started building a battery cell plant in Vietnam so Vinfast can own its battery supply chain. The company is looking to initially produce 100,000 battery packs per year with $174 million of investments and then upgrade its capacity to one million. Vinfast became Vietnam"s first fully fledged domestic car manufacturer when its gasoline-powered models built under its own badge hit the streets in 2019. It began selling EVs in Vietnam at the end of 2021.