Chrysler LLC used unmarked test cars, a secret budget and covert engineering to pull off last month's surprise unveiling of three electric vehicles, thrusting itself into the competition between General Motors and Toyota for fuel-efficiency bragging rights.

In January 2007, with a mandate from then-Chief Executive Officer Tom LaSorda to produce working prototypes by this summer, Chrysler plucked designers and engineers from around the company to work in a secluded area of the automaker's Auburn Hills, Mich., headquarters, said Doug Quigley, the chief engineer on the project. Chrysler announced the vehicles on Sept. 23, saying one of three models will be on sale in 2010.

''We were completely shocked here,'' said Tracy Handler, an automotive product analyst at Global Insight Inc. in Troy, Mich. ''And probably skeptical a little bit as to how real these are.''

Until the announcement, Chrysler rarely figured in industry electric-car buzz, dominated by GM's Chevrolet Volt, due in 2010, and Toyota's planned plug-in version of the gasoline-electric Prius, which has helped the Japanese automaker snare 77 percent of the U.S. market for hybrid vehicles.

Chrysler's initial electric-car fleet consists of a Jeep Wrangler, Town & Country minivan and a two-seat sports car called, for now, the Dodge EV, based on a Group Lotus Plc Europa design.

Developing prototypes is one thing. Whether a money-losing automaker one-quarter the size of GM and Toyota can assemble competitive advanced electric vehicles as collapsing sales reduce revenue is another.

In addition to the Volt, which GM says will travel 40 miles on an initial charge, Japanese-based Nissan plans to sell an all-electric car with a 100-mile range, also in 2010. Toyota hasn't given a target date for the plug-in Prius.

Chrysler used existing models to speed the project along. The tradeoff is the vehicles might lack the weight-savings and aerodynamics GM's Volt has promised as an all-new design, Quigley said. Those improvements will go into Chrysler's next generation models, already in development, he said.

It will be ''interesting'' to see how Chrysler accomplishes the power needs for a vehicle the size of a minivan, said David Darovitz, a GM spokesman in Detroit.

John Hanson, a Toyota spokesman in Torrance, Calif., said new zero-emission vehicle regulations imposed by the California Air Resources Board makes it necessary for the largest automakers to sell some kind of super-low emissions vehicle, such as an electric car, starting in 2010.

''They have to come out with something,'' he said of the Chrysler project.

Robert E. Nardelli kept the project alive after replacing LaSorda as Chrysler CEO. He authorized the team to bypass the normal procurement process for parts to accelerate development, Quigley said. The program was named ''ENVI,'' which is pronounced like envy, for ''Environment,'' according to Chrysler spokesman Todd Goyer.

Prototypes, with their electric motors concealed inside the bodies of existing models, went unnoticed on test tracks and around Chrysler headquarters, said Lou Rhodes, president of the electric-car unit. The development team, which grew to ''several hundred'' employees, worked in isolation on half a floor within Chrysler's restricted-access design center, said Rhodes.

The company, privately owned since its purchase by Cerberus Capital Management LP in August 2007, won't say how much it is spending on the project.

It has a $3 billion annual capital budget that includes new product development and is hiring engineers and designers for the program even after announcing the layoffs of more than a third of its work force since 2007.

Detroit-based GM has said it will spend at least $500 million building the Volt.