NEW YORK - U.S. emissions of carbon dioxide, the main greenhouse gas blamed for global warming, should fall 6 percent in 2009 as the recession curbs electricity demand, the government forecast on Wednesday.

The Energy Information Administration's monthly forecast saw a bigger drop in 2009 emissions than it did in its August forecast, which said output would fall 5 percent.

The EIA, the statistics arm of the Department of Energy, projected the drop because of the weak economic conditions and declines in the consumption of most fossil fuels.

Despite the recession-related drop, the United States will remain by far the largest polluter on a per capita basis of greenhouse gases. For total emissions, the United States is second, behind China.

President Barack Obama's goal of cutting emissions from 2005 levels by 2020 will remain a challenge. The EIA said carbon emissions should rise 0.9 percent next year as the economy recovers. In August, the forecast was for an increase of just 0.7 percent in 2010.

Total U.S. energy-related carbon dioxide emissions, which represent about 80 percent of overall U.S. greenhouse gas output, jumped nearly 16 percent from 1990 to 2008, the EIA said in May.

Demand for coal, which emits about twice as much carbon dioxide as natural gas per unit of energy, should fall nearly 10 percent in 2009 helped by fuel switching, the EIA said.

Natural gas prices plummeted to 7.5 year lows in recent weeks amid new field discoveries and weak global demand.

(Reporting by Timothy Gardner; Editing by David Gregorio)