California Gov. Arnold Schwarzenegger's plan for a statewide network of hydrogen fueling stations for fuel cell cars has stalled.

Schwarzenegger promised four years ago that hundreds of stations would be built across California but not a single hydrogen fueling station has been built under the program, the San Jose Mercury News reported Tuesday.

The newspaper said there are only 175 vehicles in California running on hydrogen and nearly all of those are in government fleets.

Mary Nichols of the state Air Resources Board said the hydrogen fueling station program is still on track.

"Hydrogen vehicles are definitely going to be part of our future," she told the newspaper. "They are just not as big a part today as was hoped in 2004."

Fuel cells produce electricity by taking in oxygen and hydrogen and using electrons to create an electrical current that powers a vehicle's motor, the newspaper said.