Republican activists sharpened their party's opposition to gay marriage Wednesday, a day after Vice President Cheney defended such unions. The action was among several steps conservatives took to firmly place their stamp on the GOP platform ahead of next week's convention, whose long list of moderate speakers has irked some on the party's right flank.

On the first of two days of platform hearings and votes, Republican delegates reaffirmed long-standing planks on bills that have stalled in Congress, such as allowing prayer in public schools and amending the Constitution to ban abortion.

They added a second proposed constitutional amendment, to bar same-sex marriage, which President Bush embraced this year. At the urging of conservative groups such as the Family Research Council, the platform committee went further in tone and detail than the GOP staffers who wrote the draft.

The marriage section condemns "a few judges and local authorities" who presume to change "the most fundamental institution of civilization." It says same-sex couples should not receive legal benefits set aside for married couples, and it calls on the Senate to join the House in voting to strip federal courts of the authority to overturn state laws banning gay marriage.

The "protecting marriage" plank's adoption stirred little debate in a morning subcommittee session that added two amendments, and no debate in the evening session of all 110 members of the platform committee.

It came a day after Cheney told a questioner at an Iowa forum that Americans should be free to enter "into any kind of relationship they want to." Cheney, who noted he has a gay daughter, made similar comments in 2000. But the Iowa remarks sparked controversy because they put him at odds with Bush only days before the Republican convention opens here.

Conservative groups, already working closely with platform delegates, pounced on Cheney's comments. Tony Perkins, president of the Family Research Council, told reporters that Cheney's remark "makes it seem the administration is split on the issue." Gary L. Bauer, president of the group American Values, said Cheney's statement "runs the risk of demoralizing the very people the president and vice president desperately need to be reelected." Perkins and Bauer hailed the platform language on gay marriage, which they said their groups had helped write.

Some moderate Republicans were fuming, however, saying the party was turning its back on potential swing voters from the political center. Christopher Barron, spokesman for the gay group Log Cabin Republicans, called the subcommittee's action "mean-spirited" and "a slap in the face to fair-minded Republicans."

Meanwhile, Republicans who support abortion rights again failed to persuade platform writers to drop the call for a constitutional ban on abortions, which has been an official GOP plank since 1976. "The Republican Party has lost a tremendous opportunity" to appeal to the majority of Americans who support legalized abortion within certain limits, said Jennifer Blei Stockman, co-chairman of the Republican Majority for Choice.

The moderate groups also failed to persuade platform writers to embrace what they termed a "party unity plank," which would state that the party realizes that "Republicans of good faith" may disagree with the planks on abortion, gay rights and other issues. The 110 delegates instead approved a more general declaration that the GOP is the "party of the open door" and it accepts members with "differing positions." The statement does not specify abortion or any other areas of disagreement.

On stem cell research, the subcommittee on "strengthening our communities" endorsed Bush's decision to allow federal funding for a limited number of cell "lines" derived from five-day-old human embryos. Many scientists, and Democrats including presidential nominee John F. Kerry, say the limits are impeding possible breakthroughs in treating diseases such as Parkinson's.

The platform makes no nod toward giving the District of Columbia voting rights in Congress, saying the District "should remain independent of any individual state."

The platform committee chairman, Senate Majority Leader Bill Frist (R-Tenn.), acknowledged that some conservatives are displeased with the convention's prime-time lineup of speakers who support abortion rights and other moderate policies. They include New York City Mayor Michael Bloomberg, former mayor Rudolph W. Giuliani, New York Gov. George E. Pataki, California Gov. Arnold Schwarzenegger and Sen. John McCain (Ariz.).

"This is our conservatives' first shot at the [platform] committee," Frist said moments before the subcommittees began deliberating. Although platforms are nonbinding -- and candidates often ignore them -- the party's final document "will live on much longer than the spoken word," he said.

Frist sought to play down divisions that resonated outside the five subcommittee hearings in the Jacob K. Javits Center during the morning session. He said Cheney's comments in Iowa demonstrate that "diversity is a strength in the majority party." The platform committee was scheduled to conclude its work on the 100-page document Thursday and offer it for the convention's adoption next week.