WASHINGTON – The Senate endorsed President Bush’s climate-change policies Tuesday, 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 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. Sens. Olympia Snowe and Susan Collins, R-Maine, voted against the measure.

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

A vote on that proposal, offered by Sens. John McCain, R-Ariz., and Joe Lieberman, D-Conn., was scheduled for Wednesday. 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 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 told The Associated Press.

“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 greenhouse emissions and 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 expressed support for 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.

It would establish a system of loan guarantees and provide other incentives to spur private companies to develop technologies that would capture carbon or promote development of cleaner coal and other fuels. Hagel acknowledged the energy bill already contains incentives for such programs, but he said his proposal would focus more closely on emissions affecting climate.

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 that have been off limits to energy development since the 1980s.

“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.