According to recent vehicle sales more Americans are willing to buy cars that have eco-friendly hybrid engines. Figures show that registrations for hybrid vehicles has risen by nearly 26 per cent.

Analysts say the increase is mainly due to rising gasoline prices and the fact that more hybrid models are becoming available to the consumer.

Ford, Honda and Lexus have all announced plans to increase the number of hybrid cars in their product ranges.

The most popular model is Honda's Civic, which accounted for 50 per cent of the sales last year.

Lonnie Miller, director of automotive analyst company Polk, said: "People are buying hybrids because of mileage benefits and environmental concerns. With the rising cost of gas, hybrid registrations will likely increase in 2004."

Some states are encouraging more hybrid vehicles sales by offering tax breaks to residents. For example Minnesota has introduced legislation that gives allows sales tax exemption for those buying certain hybrid models.

However hybrid cars are still in the minority with the total number being sold just 43,435, a mere fraction when compared to total vehicle sales of 16.7 million.

Hybrid vehicles represent one of the possible technologies for future emissions controls, along with diesel filter technology and catalytic converters.