The White House is reviewing a finding by the U.S. Environmental Protection Agency that global warming is a threat to public health and welfare.
The EPA's action is the first step to regulating carbon dioxide and other greenhouse gases under the Clean Air Act, a move that would have broad economic and environmental impacts.
Congressional officials familiar with the EPA's views say the agency's finding was sent to the White House Office of Management and Budget for review.
Two years ago, the U.S. Supreme Court said if greenhouse gases are found to endanger public health or welfare, then they must be regulated. But the Bush administration refused to make such a finding.
The budget office provided no details but acknowledged it received the EPA document last Friday.