Ford will build a Mercury Mariner hybrid SUV for the 2007 model year. The Mariner will join the Ford Escape SUV and a future midsize sedan in the automaker's hybrid program.

Ford, the No. 2 U.S. automaker behind General Motors Corp., was scheduled to announce the Mariner addition Wednesday during media previews at the New York International Auto Show.

Ford unveiled the Escape hybrid last year at the New York show and plans to begin selling the vehicle this summer. Ford has said the hybrid system in the front-wheel-drive Escape allows the vehicle to get 35 to 40 miles per gallon in city driving, compared with 20 miles per gallon in a 2005 Escape with a V6 engine.

A similar hybrid system will be available in an upcoming Ford midsize sedan, also introduced at last year's New York show. Ford had planned to call the model Futura, but a federal court has ruled that the Pep Boys auto parts retail chain owns the rights to that name.

Ford has not announced a definitive launch date for the hybrid version of the sedan.

Dan Becker of the Sierra Club said the new hybrid proves automakers can make big vehicles with better gas mileage. The Sierra Club had been critical of Ford since the automaker last year backed away from a promise to improve fuel efficiency in all of its SUVs by 25 percent by mid-decade.

"If they can make an SUV get 40 miles to the gallon, they can make all their vehicles much cleaner and cut our oil dependence, and we encourage them to do so," Becker said Tuesday.

Hybrids draw power from two different energy sources, typically a gas or diesel engine combined with an electric motor. For now, the only versions available in the United States are small cars made by Honda Motor Co. and Toyota Motor Corp., but nearly every automaker is investing in hybrid technology.

Toyota, Japan's biggest automaker, was the first in the world to commercially mass-produce and sell hybrid cars with the Prius in 1997. Its luxury Lexus division is scheduled to begin selling a hybrid SUV later this year.

Ford has touted the Escape hybrid as the world's first "no-compromise SUV," combining the fuel economy benefits of a "full" hybrid along with the cargo capacity and on- and off-road capabilities of the traditional Escape.

Pricing for the Escape hybrid has not been released.

Ford also is expected to announce in New York that Mary Ann Wright, chief engineer of the Escape hybrid, will lead a new group as director of Ford's sustainable mobility technologies and hybrid vehicle programs. The group will be responsible for all of Ford's fuel-cell and hybrid vehicles.

GM said late last year it will focus its most advanced hybrid technology on its largest, least-fuel-efficient models first. The automaker said it also had scrapped plans to place a full-hybrid engine in a future compact sport utility vehicle.

The first of the automaker's advanced hybrids - those that can achieve a fuel-economy impprovement of up to 35 percent, compared to one-third that amount with mild systems - is scheduled to reach showrooms in 2007.

Even as the popularity of hybrids grow, automakers have said gas-electric engines are a transitional technology that will eventually be replaced by hydrogen-powered fuel cells that emit exhaust containing nothing more toxic than pure water.

However, experts say the nation is at least a decade or two away from that, as the infrastructure needed to fuel up with hydrogen is virtually nonexistent.

Ford, like others, is working on long-term research related to hydrogen-powered vehicles. The work includes a Ford Focus with a hydrogen internal combustion engine and a hydrogen hybrid research vehicle.