On the first day of the Copenhagen climate change conference the U.S. Environmental Protection Agency has found that greenhouse gases constitute a threat to human health–a prerequisite for the agency to start regulating the gases.

The timing of the announcement is intended to boost efforts to reach a climate change agreement at the conference. Many countries have criticized the lack of action on climate change from the U.S., but now U.S. negotiators have an argument that their country is taking greenhouse gases seriously. If Congress fails to legislate for greenhouse gas emissions reductions, the EPA will step in.

“Today’s action is a step towards enduring, pragmatic solutions to the enormous challenge of climate change,” EPA administrator Lisa Jackson said (according to a copy of her speech). “It also means that we arrive at the climate talks in Copenhagen with a clear demonstration of our commitment to facing this global challenge. We hope that today’s announcement serves as another incentive for far-reaching accords in our meetings this week.”