The pollutants from electricity generating plants have been linked to asthma attacks and other respiratory illnesses.

Vermont Sen. Jim Jeffords, an independent who chairs the panel, placed himself on a collision course with the Bush administration by proposing a 23-percent reduction in carbon dioxide emissions by 2008.

Thursday's vote was the culmination of negotiations with lawmakers, green groups and industry that began last year.

"Today's action sends a clear message to this administration that the Senate is willing to engage on clean air and climate change," Jeffords said.

The Bush administration has vehemently opposed any cap on carbon dioxide emissions on the grounds the cost of complying would be devastating to U.S. industry.

Earlier this month, the administration quietly released a report that affirmed the probable harmful effect of greenhouse gases, which are on the rise from human activities, but President George W. Bush dismissed it as a product of the "bureaucracy."

Republican opposition to the bill will weigh heavily on its prospects for approval by the full Senate, even though Majority Leader Tom Daschle has indicated support.

Without major revisions, a Senate vote is unlikely before Congress adjourns in early October, a congressional aide said.

"This bill is dead," Republican Sen. George Voinovich said in a statement, calling Jeffords' decision to press forward on a committee vote a "political charade."

"The votes are here on the committee ... but they're not there on the Senate floor," said Robert Smith, a New Hampshire Republican. "They're not even close."

Jeffords said the bill can survive a Republican assault.

"I do not agree that all hope is gone," Jeffords told reporters, adding he expects 52 senators to support his bill.

That is short of the 60-vote minimum needed under Senate rules to end a filibuster and allow a vote on the measure. But Jeffords said he was heartened by indications from some panel Republicans that action on carbon dioxide is needed.

Phil Clapp, president of the National Environmental Trust, called the vote a "historic first step on global warming."

Also, the bill would cut emissions of acid rain-causing sulfur dioxide and smog-forming nitrogen oxides far beyond the levels proposed by the White House in February. The legislation also would set first-time limits on mercury emissions.

U.S. utilities are trying to cut emissions, but the Senate bill sets an untenable pace, said the Edison Electric Institute, an industry group. "The question isn't whether we make further reductions, but rather how far we go and how fast," said Quin Shea, executive director of the institute.

WHITE HOUSE SUBPOENA DELAYED

Separately, Jeffords backed off his threat to call a vote to subpoena the White House for documents about its decision to relax air pollution rules for aging coal-fired power plants.

Jeffords said would give the administration more time after receiving assurances from the Environmental Protection Agency that it would turn over some documents by July 3.

However, subpoenas could still be issued if the administration does not cooperate, he said.

"The administration continues to have concerns about providing certain pre-decisional documents to Congress" before the rules have been finalized, EPA Administrator Christine Todd Whitman wrote to Jeffords in a letter dated June 27.

Jeffords opposes changes in the administration's so-called "new source review" regulations to give old utilities and refineries more leeway in repairing and expanding old plants without buying costly equipment to control air emissions.