WASHINGTON -- The Senate endorsed President Bush's climate-change policies yesterday, approving a measure that avoids mandatory reductions of heat-trapping pollution while still boosting government support for cleaner energy sources.

In a second setback for environmentalists, the Senate also agreed to conduct an inventory of offshore oil and gas resources that some senators called a prelude to drilling in coastal waters now off limits to energy development. An attempt to strip the inventory from a broad energy bill failed 52-44.

On climate change, Republicans rallied around a measure offered by Sen. Chuck Hagel, R-Neb., that would rely on voluntary industry measures to slow down the growth of heat-trapping emissions through an expansion of "private-public partnerships" to develop ways to produce energy with lower carbon emissions.

Carbon from burning fossil fuels is the principal heat-trapping gas that many scientists believe is warming the Earth.

The Hagel amendment was approved 66-29 and inserted into the energy legislation that Senate leaders hope to finish this week.

Among regional lawmakers, voluntary industry measures were supported by Sens. Arlen Specter and Rick Santorum, both R-Pa.; Mike DeWine and George Voinovich, both R-Ohio; and Jay Rockefeller, D-W.Va. They were opposed by Sen. Robert Byrd, D-W.Va.

Senators later began debate on a more ambitious climate-change measure that would require industry and power companies by 2010 to reduce heat-trapping emissions -- mainly carbon dioxide from burning fossil fuels -- to levels they were five years ago.

A vote on that proposal, offered by Sens. John McCain, R-Ariz., and Joe Lieberman, D-Conn., was scheduled for today. It was given slim chance of being approved. A third proposal, billed as a compromise, was abandoned by Sen. Jeff Bingaman, D-N.M., after it became clear that it would get scant GOP support.

McCain and Lieberman argued that mandatory measures were needed to get industry to reduce its flow of heat-trapping pollution into the atmosphere. McCain called Hagel's measure "meaningless" because it has nothing to force industry to make greenhouse emission reductions.

"We've gone from outright opposition [to mandatory reductions] to a fig leaf," he said.

"It will do nothing to reduce our greenhouse gas emissions," Sen. Dianne Feinstein, D-Calif., said of the Hagel amendment, arguing that the McCain-Lieberman proposal was "the real climate amendment."

The Bush administration has opposed regulating carbon or other greenhouse gases, contending that voluntary actions by industry are already reducing the growth of emissions and that to go further would harm the economy and raise energy prices.

"The McCain-Lieberman amendment will put coal out of business," said Sen. George Voinovich, R-Ohio, as he supported the Hagel proposal.

Hagel described his measure as "a market-driven, technology-based approach" to dealing with climate change without imposing mandatory emission-reduction requirements on industry. Yet it will dampen the growth of greenhouse gases both in the United States and in developing countries, he said.

Environmentalists have dismissed Hagel's approach, saying it would do little to move climate policy beyond what the Bush administration is doing: relying on voluntary industry measures and focusing only on slowing the growth of greenhouse emissions, not reducing those emissions.

The inventory of oil and gas resources beneath the nation's Outer Continental Shelf was strongly criticized by some coastal senators, who said it would lead to drilling in areas where energy development has been barred since the 1980s.

Among regional lawmakers, the inventory was endorsed by Specter, Santorum, DeWine, Voinovich and Byrd. It was opposed by Rockefeller.

"It's the first step to drilling. It's the proverbial camel's nose under the tent," declared Sen. Bill Nelson, D-Fla., who said the Interior Department already is conducting an inventory of offshore energy resources every five years.

Proponents of the inventory said the country needs to know what offshore oil and gas resources might be available in future years. "This gives Americans full information of what is there," said Sen. Mary Landrieu, D-La. "This is not a drilling amendment."

Oil and gas development has been banned for more than two decades in almost all of the country's coastal acreage outside the western Gulf of Mexico. Congress enacted the first moratorium in 1981 and later expanded its reach and reaffirmed it every year. A succession of presidents have continued the moratorium since 1990. The latest extension, issued by President Bush, expires in 2012.