An environmental group that has endorsed John Edwards said Friday it's airing a radio ad challenging Sen. Hillary Clinton, D-New York, to oppose a global warming bill in Congress.

The group, Friends of the Earth Action, says the bill would give $750 billion to "corporate polluters" and, while praising Edwards' opposition of the measure, urges people to call Clinton and ask her to oppose it.

The ad prompted Clinton's campaign to blame Edwards for the ad, calling it the first negative spot of the campaign season.

The bill, which is sponsored by Sens. Joe Lieberman of Connecticut and John Warner, R-Va., has ignited debate on both ends of the political spectrum. It requires sharp cuts in emissions, but some environmental groups say it doesn't go far enough. Its method of controlling emissions also has come under fire.

Conservatives also have been critical, saying the bill would hit consumer pocketbooks.

Edwards already has said he's against the measure, which could come before a Senate committee next month. Clinton is a member of the panel.

Asked her position on the bill Friday, Mark Daley, a Clinton spokesman, said: "John Edwards must be getting desperate if he's allowing an anti-ethanol group to go on Iowa radio and run the first negative ad of the campaign on his behalf."

Edwards' camp responded to Clinton's complaint by citing past votes against ethanol mandates. She supports expanded ethanol use now.?"We would hope that the Clinton campaign would respect caucusgoers enough to explain their position on the bill before they attack someone else," said Dan Leistikow, an Edwards spokesman.

Friends of the Earth responded to President Bush's call for greater ethanol use in January by warning greater use of corn ethanol would damage the land and environment. It urged the bulk of a new renewable fuel portfolio go to?"environmentally friendly fuel sources" like switchgrass.

The radio ads will air in Cedar Rapids and Des Moines. The ad does credit Clinton for proposing an energy and global warming plan of her own but says?the Lieberman and Warner bill will give billions to "the very companies polluting our air and causing global warming." It says Edwards has been "courageous" to oppose it and urges people to call Clinton and ask her to "fix or ditch" the measure.

Sen. Tom Harkin, D-Iowa, also is a co-sponsor.

Contact Ed Tibbetts at (563) 383-2327 or etibbetts@qctimes.com.