WASHINGTON - The U.S. Environmental Protection Agency formally declared that greenhouse gases endanger human health Monday, allowing President Barack Obama to show his commitment to act as a major climate change summit opened in Copenhagen.

The ruling by the EPA, widely expected after it issued a preliminary finding earlier this year, will allow the agency to regulate planet-warming gases even without legislation in the U.S. Congress.

It will also inject some optimism into the two-week global meeting on controlling climate change in the Danish capital.

Business groups said the move, which could allow regulation of gases from vehicle tailpipes or smokestacks, would hurt the economy and jobs just as the country is emerging from a deep recession.

They say the regulatory route could be even more damaging than legislation, mainly because they have less influence over the EPA than over Congress.

But U.S. Energy Secretary Steven Chu said the decision would ultimately benefit American industry.

We will live in a carbon-constrained cooperative world, Chu told CNBC. And the United States has the ability to lead in creating these new technologies that can give us the energy we need with the low carbon emissions, or we can follow. If we lead, that will add to our economic prosperity.

The EPA ruling applies to six gases scientists say contribute to global warming, including the main one, carbon dioxide.

(Additional reporting by Ayesha Rascoe, Roberta Rampton and Tom Doggett; Editing by Simon Denyer and David Storey)