With world governments failing to agree to reductions in the production of greenhouse gases, the outgoing United States energy secretary Bill Richardson has made it clear that he does not favour government action to help his country's car drivers move towards environmentally friendlier cars.

Speaking in Montreal at the annual meeting of the Electric Vehicle Association, Mr Richardson acknowledged that pickup trucks and sports utility vehicles were the fastest growing sector of the country's transportation sector in terms of fuel consumption, and that cars trucks and buses accounted for a third of the country's carbon dioxide emissions.

In an interview afterwards Mr Richardson rejected the idea that greater regulation could help encourage greater fuel efficiency, saying instead that he felt the way forward was through the government's research projects with the big three auto-makers - Ford, DaimlerChrysler and General Motors.

"We favour joint partnerships and gentle persuasion, and I think they have worked - we may be close to some major breakthroughs which will enable drivers to have their SUVs but with fuel efficient engines."

All three auto-makers say they are close to producing a hybrid version of an SUV in the next few years - a car with an electric engine for low speeds when petrol ones are least efficient, and with a petrol engine and energy from braking to charge up the battery. Current saloon models, (such as the Toyota Prius just launched in the US and Europe), are around 50% more fuel efficient than petrol equivalents.