Toyota plans to introduce its plug-in hybrid electric vehicle late this year, a year earlier than originally planned, and a year ahead of the Chevrolet Volt, a senior Toyota executive said on Sunday.

James Lentz, the president of Toyota Motor Sales U.S.A., said in an interview that Toyota planned to initially make about 500 plug-in hybrids, which will be made available first to commercial customers. About 150 plug-ins will be slated for customers in the United States, Mr. Lentz said.

His comments came at the North American International Auto Show in Detroit, which opened to the press on Sunday.

At last year’s show, Toyota’ s president, Katsuaki Watanabe, said Toyota planned to introduce a plug-in hybrid vehicle in 2010. The plug-in, which can be re-charged by plugging it into a wall outlet, will join a lineup of other hybrid-electric vehicles sold by Toyota, including the Prius. Toyota will show a new version of the Prius here on Monday.

G.M. says it plans to introduce its plug-in Volt by late 2010. The Volt, which will be made at a plant in Detroit, and powered by a lithium-ion battery, is the centerpiece of G.M.’s efforts to market environmentally friendly cars.

The Toyota plug-in hybrid will be built in Japan, where Toyota also builds the Prius. The first plug-ins will be essentially built by hand, said Masami Doi, Toyota’s general manager of its global strategic planning department.

The plug-ins also will be powered by lithium-ion batteries, Mr. Lentz said, unlike the Prius, which will continue to be powered by a nickel-metal hydride battery. The lithium-ion batteries will be produced in Japan by Panasonic, which also makes batteries for the Prius, Mr. Doi said.

G.M. unveiled the Volt as a concept car at the Detroit show in 2007, beating Toyota with word that it was developing a plug-in hybrid. Mr. Lentz did not say why Toyota had sped up its program, which has been a major project within the carmaker.

But if Toyota stays on its new schedule, it will win at least a psychological advantage over G.M., said Andrew Shapiro, an industry analyst with the Casesa Shapiro Group.

“G.M. announced it first, and Toyota gets it to the market first,” Mr. Shapiro said.

Mr. Lentz sought to play down any impression that Toyota was in a race with G.M. The initial Toyota plug-ins will not be available to individual consumers, unlike the Volt, which G.M. says will go on sale to the public at the end of 2010.

“I don’t consider that they will be on the market yet,” Mr. Lentz said.

Mr. Lentz said the first Toyota plug-ins will be provided to commercial customers like utility companies, corporations and others where their use can be carefully monitored. “We’ll learn how they’re used, and where people want to re-charge them,” like office versus home charging stations, he said.

Toyota also can study “the trade-offs between performance and range” meaning the miles the car can travel before its battery needs to be recharged, he said.

Mr. Shapiro said the strategy of providing plug-ins to fleet users first would give Toyota information that its engineers can use to improve the vehicle before the Volt arrives. “They’ll have a year’s worth of real world feedback. That will be invaluable, because they can make changes quickly,” Mr. Shapiro said.