* Texas suit one of several to challenge EPA

* EPA pursuing CO2 rules if Congress does not act (Adds byline, American Petroleum Institute petition, others)

DALLAS, Feb 16 (Reuters) - Texas and several national industry groups on Tuesday filed separate petitions in federal court challenging the government’s authority to regulate U.S. greenhouse gas emissions.

Texas, which leads U.S. states in carbon dioxide emissions due to its heavy concentration of oil refining and other industries, will see a major impact if U.S. mandatory emissions reductions take effect.

In December, the Environmental Protection Agency ruled that greenhouse gases like carbon dioxide endanger human health, opening the door for the agency to issue mandatory regulations to reduce them.

Texas said it had filed a petition for review challenging the EPA’s “endangerment finding” with the U.S. Court of Appeals for the D.C. Circuit. Texas has also asked the EPA to reconsider its ruling.

“The EPA’s misguided plan paints a big target on the backs of Texas agriculture and energy producers and the hundreds of thousands of Texans they employ,” Texas Gov. Rick Perry said.

The National Association of Manufacturers, the American Petroleum Institute, and the National Petrochemical and Refiners Association also said on Tuesday they filed a petition challenging the EPA in federal appeals court.

The U.S. Chamber of Commerce and U.S. iron and steel makers have also signaled they would file lawsuits.

Environmental groups said Texas should focus on building cleaner energy sources instead of filing lawsuits.

“Governor Perry should win an Olympic medal for taking the environment downhill,” said Luke Metzger at Environment Texas. “Global warming is the greatest environmental threat facing Texas and the planet and Governor Perry’s obstructionism puts the state at great risk.”

Conservative Republicans like Perry have been sounding the alarm of job losses in the debate over regulating greenhouse gas emissions -- a hot-button issue at a time of high joblessness and economic uncertainty.

The EPA is threatening to regulate carbon emissions if Congress does not. In June, the House of Representatives narrowly passed a cap and trade bill that would allow industry to buy and trade pollution permits, but the legislation has stalled in the Senate.

President Barack Obama would rather have Congress pass a bill that could provide more protections for industry while also controlling pollution. But he is using the threat of EPA regulation to encourage lawmakers.

Some prominent Senate Democrats have predicted that comprehensive climate control legislation, including a cap-and-trade mechanism, will not pass this year.