Bush, who opposes mandatory caps on emissions, said in a statement on Wednesday night that this report puts his program for reducing greenhouse gas intensity -- the amount of emissions per unit of economic growth -- "well ahead of what is needed" to meet the White House goal of cutting this figure by 18 percent by 2012.

His comments came ahead of a Group of Eight meeting in June where rich countries are expected to discuss global warming.

German Chancellor Angela Merkel has signaled she will urge the G8 to slash greenhouse emissions that spur global climate change.

However, the United States rejects key targets and timetables for combating global warming, including a pledge to halve emissions by 2050, and wants to cut these ideas from a draft summit communique seen by Reuters.

MIGHTY EFFORTS NEEDED

Scientists say greenhouse gas emissions could bring deadly heat waves, flooding and droughts.

The 2006 dip in emissions may have been caused more by unpredictable events like weather than by intentional efforts to curb carbon dioxide, the EIA report said.

Moderate US winter temperatures and relatively moderate prices for clean-burning natural gas helped cut the emissions, according to the report.

Warm weather "ain't a good strategy to rely on as your way to reduce emissions," Dan Becker, the head of the Sierra Club's climate program, said in a telephone interview.

David Doniger, director of the Natural Resources Defense Council's climate center, said reducing greenhouse gas intensity is not a good goal. It would fall even if the government took no action because industries have become more energy-efficient since the high oil prices of the 1970s, he said.

"If we just keep playing up this voluntary approach, where the only things being done are weather changes or economic fuel price changes, you might see an occasional year where emissions go down. But the overall trend is going to be up, up, up," said Doniger.