A key Republican lawmaker announced last night that he is not ready to support compromise legislation setting mandatory limits on emissions of gases linked to global warming.

The decision by Sen. Pete V. Domenici (N.M.), chairman of the Energy and Natural Resources Committee, threw into question the future of legislation sponsored by Sen. Jeff Bingaman (D-N.M.).

The measure, which Bingaman has said he would introduce as an amendment to the energy bill, has been gaining momentum in the Senate despite opposition from the Bush administration.

Aides to Domenici said last week that he was considering co-sponsoring the bill, which would have increased its prospects for passage. But last night, Domenici said in a statement that more time is needed to hold hearings and consider the matter.

"It became clear that we do not have something ready to be added to the energy bill," the statement said. "This is just too tough to do quickly."

The Bingaman plan would cut emissions of greenhouse gases by 2.4 percent per unit of economic growth beginning in 2010. Companies that go beyond those levels would be required to buy permits. The price of the permits would be limited.

Bingaman's proposal mirrors the recommendations of the bipartisan National Commission on Energy Policy, whose members include environmentalists and industry representatives.

The amendment was seen as a compromise because the plan is less strict than one crafted by Sens. John McCain (R-Ariz.) and Joseph I. Lieberman (D-Conn.). Their legislation, expected to be offered today, would establish an emissions cap-and-trade system that, in the worst-case scenario, would in 2010 freeze emissions of greenhouse gases at levels existing at that time.

Sen. Chuck Hagel (R-Neb.) plans to introduce an amendment seeking voluntary limits and aims to cut emissions by offering incentives for technological development and climate research.

The Bush administration opposes mandatory limits, favoring a voluntary approach instead. The White House says mandatory restrictions could result in higher energy prices, the loss of jobs and slower economic growth.

Energy legislation approved by the House in April included no such restrictions. The House has signaled opposition to mandatory limits.