The three Senate sponsors of climate and energy legislation now plan to unveil their proposal on April 26, aides said, a few days later than expected, but in time for potential floor debate before the Senate adjourns for its annual summer recess.

Senators John Kerry, Democrat of Massachusetts, Lindsey Graham, Republican of South Carolina, and Joseph I. Lieberman, Independent of Connecticut, have been laboring for months to paste together a comprehensive measure that can win 60 votes.

They have spent countless hours with their colleagues trying to fashion a compromise that addresses the varied regional and ideological strains of the Senate. President Obama has offered guidance and assistance from the sidelines, introducing proposals on clean coal research, nuclear loan guarantees and offshore oil drilling in hopes of attracting support for the measure.

Mr. Kerry has said that the bill will try to achieve about a 17 percent reduction in greenhouse gas emissions from 2005 levels by 2020, the same target as legislation passed by the House last year and pledged by Mr. Obama at an international climate conference in Copenhagen in December.

After the bill’s introduction, the Environmental Protection Agency and the Congressional Budget Office will produce studies of its costs and effectiveness, a process that will take as much as six weeks.

Senator Harry Reid, the Democratic leader, has promised to find time for floor debate on the energy measure in a crowded legislative calendar that includes a broad financial regulation measure and confirmation hearings for a Supreme Court nominee.

Senate Republicans have offered little encouragement to the bill’s  sponsors, and a critical group of Midwestern Democrats have raised a number of concerns about the bill’s impact on manufacturing, jobs and energy prices.