By DINA CAPPIELLO Associated Press

WASHINGTON (AP) - The head of the Environmental Protection Agency on Wednesday goes before a House committee that is determined to block her agency's steps to address climate change.

Lisa Jackson faces questions on the EPA's attempt to curb the release of gases blamed for global warming. New legislation to reduce greenhouse gases failed in Congress last year. Now the administration is left to use existing law to achieve its goals.

Jackson contends the law and scientific evidence on global warming give her no choice but to act. Republicans contend using existing law will penalize industries that otherwise could be creating new jobs, and they've made the agency a central target of their anti-regulatory agenda.

Lawmakers of both parties have already introduced a dozen bills aimed at weakening, delaying or blocking pollution regulations.