Fields said there were also key policy and regulatory hurdles to clear. He said viable, mass-market plug-ins will take substantial government investment in research and that near-term prospects for making a "business case" are limited.
Fields said Congress must allocate money already approved for research programs dedicated to developing powerful, reliable and affordable batteries, the crucial energy component.
He also said government should approve tax credits - similar to ones offered today for consumer purchases of gas/electric hybrids. Government should also help retool factories to build plug-ins, Fields said.
"Japan, China, Korea, and India are significantly funding the research development and deployment of plug-in hybrid vehicle technologies. This is a race we must win," Fields said.
Ford and other U.S. auto manufacturers are reeling financially from sinking sales of gas-guzzling sport utility vehicles and pickup trucks with domestic gasoline prices topping $4 a gallon this month.
Domestic automakers have also trailed Japanese rivals, such as Toyota Motor Corp, in producing mass market hybrids.
Ford is now partnering with Southern California Edison and the Electric Power Research Institute to build 20 plug-in hybrid sport utility vehicles on a demonstration basis.
An Escape SUV delivered by Ford to the U.S. Energy Department runs on electricity and gasoline or E85, a mostly ethanol fuel blend.
The Escape plug-in can run up to 30 miles at speeds under 40 miles per hour on electric power only. At higher speeds or when that battery is depleted, the vehicle switches to traditional hybrid technology. This involves another battery for use at low speeds and a flex-fuel engine for highway travel.
Flex fuel engines run on gasoline or biofuels, like ethanol or ethanol blends.