TOYOTA, Japan (AP)--Introduction of the next version of Toyota's hit Prius gas-electric hybrid won't hinge on the development of a more efficient battery called lithium-ion, a senior Toyota executive said Friday.

The executive brushed off a recent Wall Street Journal report that said Toyota Motor Corp. (TM) was delaying the launch of the next-generation Prius by a year or two because of problems in developing the lithium-ion battery. Hybrids on sale now use nickel-metal-hydride batteries.

The Toyota official, who requested anonymity, said he was puzzled by the report. He said various innovations for the next Prius are being considered - not just the lithium-ion battery.

He said some type of lithium-ion battery is preferable for hybrid vehicles in the long run because it is lighter and pack more power than nickel-metal-hydride batteries. He acknowledged that the lithium-ion battery hadn't been perfected.

But he denied that the problems Sony Corp. (SNE) had with its laptop lithium- ion batteries had alarmed Toyota about battery safety concerns, as the Journal had reported, stressing that potential battery problems were long known to Toyota engineers. Sony recalled millions of laptop batteries after reports of fires.

Competition is heating up in hybrids as gas prices soar and fears about the environment grow.

Last month, General Motors Corp. (GM) said it had signed an agreement with A123 Systems Inc., a battery maker that already produces millions of lithium-ion batteries for use in cordless power tools.

At that time, GM Vice Chairman Bob Lutz said the technology could be applied to autos, giving GM a chance to beat Toyota in the race to bring plug-in hybrid and electric cars to market.

Toyota has scored success with its hybrid vehicles, which deliver better mileage by switching between a gas engine and electric motor. Toyota has sold more than a million hybrid vehicles around the world in the past decade - more than any other automaker.

Toyota, which also makes Camry and Lexus cars, hasn't given a sales date for the remodeled Prius. The Prius, the world's most popular hybrid, first went on sale in Japan in 1997, has been revamped once and is believed to be due another makeover in the next few years.

In July, Toyota showed a plug-in hybrid for testing on public roads. A plug-in hybrid saves on gas by running longer as an electric vehicle by plugging into a regular socket for recharging.