Koei Saga, general manager of Toyota's hybrid vehicle system engineering division in Japan, says the volume is probably 100,000 vehicles a year.
"If we build 100,000 of one (hybrid) model a year, I think we would start a discussion" about a local supply base," Saga says.
Hybrids use gasoline engines and one or more electric motors to power the wheels.
Toyota's hybrid-component supply chain will remain in Japan for now.
Saga says Toyota has not yet discussed North American production of battery packs with Panasonic EV Energy Co., its battery source for all Toyota hybrid vehicles. Panasonic EV is a joint venture between Toyota and Matsushita Electric Industrial Co.
Toyota forecasts initial U.S. production of up to 50,000 Camry Hybrids a year starting late next year. It believes some of the model's content could be sourced locally when it starts production. It has not said which of those components would be sourced first.
"It's definitely not a technology we plan to leave in Japan," says Dan Sieger, spokesman for Toyota Motor Manufacturing North America.
Obtaining the necessary components will be the real restriction in how many hybrid vehicles Toyota manufacturers here, says Jim Press, COO of Toyota Motor Sales U.S.A. Inc.
Press predicted that hybrid parts will be easier to source here as other hybrid vehicles go into production around the industry.
Nissan North America Inc. is preparing to build an Altima hybrid at one of its two U.S. plants. That vehicle will rely on a Toyota hybrid powertrain.