US greenhouse gas emissions fell 2.9 percent in 2008 amid a recession and record high petrol prices, according to a preliminary estimate Tuesday from the US Environmental Protection Agency (EPA).

Lower demand for electricity and petrol helped drive down energy use over the course of the year in the US, which along with China is the world's largest polluter.

Total greenhouse gas emissions, which are blamed for global warming, have climbed nearly 13.6 percent in the US between 1990 and 2008, but emissions have fallen 2.43 percent since 2005, the EPA said.

The US pledged during the United Nations-backed Copenhagen climate summit in December to cut its emissions 17 percent below 2005 levels by 2020, and roughly 80 percent by 2050.