WASHINGTON (NYTimes) February 24, 2004 — President Bush on Tuesday declared his support for an amendment to the Constitution that would ban gay marriage, saying the union of a man and a woman is "the most fundamental institution of civilization" and that it cannot be separated from its "cultural, religious and natural roots" without weakening society.

In a five-minute announcement in the Roosevelt Room of the White House, Mr. Bush said that he was acting because "activist judges" had made aggressive efforts to redefine marriage and that preserving the institution was now a matter of national importance.

Mr. Bush said states should be permitted to have gay civil unions, even though White House officials said he would not have endorsed such unions as governor of Texas.

"The amendment should fully protect marriage while leaving the state legislatures free to make their own choices in defining legal arrangements other than marriage," said Mr. Bush, who took no questions from reporters and left the room after completing his remarks.

Mr. Bush was acting under enormous pressure from conservative supporters, who insisted that he speak out in an election year on a matter of critical importance to many of his Christian backers.

The pressure has increased in the wake of recent events in Massachusetts and San Francisco. Massachusetts is under court order to begin issuing same-sex marriage licenses on May 17 and San Francisco's City Hall has been transformed into a marriage parlor for thousands of gay and lesbian couples. Mayor Gavin Newsom of San Francisco, who authorized the issuance of marriage licenses to same-sex couples, responded defiantly on Tuesday to Mr. Bush's remarks.

Republicans said Mr. Bush was also seeking to draw a sharp distinction between himself and the Democratic front-runner in the primaries, Senator John Kerry of Massachusetts. In 1996, Mr. Kerry was one of 14 senators to vote against the Defense of Marriage Act, which defined marriage as a union between one man and one woman. Mr. Kerry opposes gay marriages but supports civil unions.

Mr. Bush's announcement, even though widely expected, immediately ignited a furious debate between conservatives who applauded it and gays who denounced it.

"It's a declaration of war on gay America," said Matt Foreman, executive director of the National Gay and Lesbian Task Force. "This is such a transparent attempt to use our lives and our families to drive a wedge into the electorate purely for political gain. I knew this was coming for a long time, but to actually read it in print, and to see him say it, left me shaking in both hurt and anger."

The Rev. Richard D. Land, the president of the Ethics and Religious Liberty Commission of the Southern Baptist Convention, embraced the decision, saying: "I'm delighted and I'm pleased, but I'm not surprised. The president's been signaling this for quite a while that he would support this if we reached the last resort. And we've now reached the last resort. Our forefathers gave us this procedure in times of crisis when the people's will is being disregarded."

Mr. Bush urged the Congress to move quickly on an amendment, which needs approval from two-thirds of the House and the Senate and then passage in at least three-fourths of the state legislatures, or 38, over a period of up to seven years.

On Capitol Hill, Senate Republican leaders said an amendment could reach the floor before November, with hearings as early as next week. But Representative Tom DeLay of Texas, the House majority leader, was more cautious about the timing.

"This is so important we are not going to take a knee-jerk reaction to this," Mr. DeLay said. "We are going to look at our options and be deliberate about what solutions we may suggest."

Republicans said Mr. DeLay, who commended Mr. Bush for his leadership on the issue, was strategically reluctant rather than ideologically to move quickly on the amendment. Mr. DeLay said on Tuesday that it would be "very difficult" to get such a measure through Congress and that some Republicans were strongly resistant to changing the Constitution.

No House or Senate advocates of an amendment have come to any agreement on its wording, though various proposals are circulating. White House officials said Mr. Bush liked the language in the only amendment introduced so far, by Representative Marilyn Musgrave, Republican of Colorado.

That proposal states: "Marriage in the United States shall consist only of the union of a man and a woman. Neither this constitution or the constitution of any state, nor state or federal law, shall be construed to require that marital status or the legal incidents thereof be conferred upon unmarried couples or groups."

Senator Kerry's chief rival for the Democratic presidential nomination, Senator John Edwards of North Carolina, does not support gay marriages either, saying instead that the government could take other steps for gay couples, like provide partnership rights and adoption rights.

Recent opinion polls have consistently found that the majority of Americans oppose gay marriage. A CNN/USA Today/Gallup poll conducted Feb. 16-17, for example, found that 64 percent thought that gay marriage should not be recognized by the law as valid.

But there is less support in opinion polls for amending the Constitution to prohibit gay marriage. In a New York Times/CBS poll in mid-December, 55 percent said they favored an amendment banning gay marriage; in the National Annenberg Election Survey in mid-February, 41 percent said they supported a constitutional amendment to prohibit states from enacting same-sex marriage.

In his remarks, Mr. Bush said he was reacting to the ruling by the Massachusetts Supreme Judicial Court, which essentially ordered the state to begin granting marriage licenses to gay couples on May 17, and to city officials in San Francisco who have issued thousands of licenses.

Those actions, he said, could have "serious consequences throughout the country." There was no assurance, he added, that the Defense of Marriage Act would not itself be struck down by "activist courts."

The only recourse, he said, was to amend the Constitution on an issue that he acknowledged reached into Americans' most private activities.

"America's a free society, which limits the role of government in the lives of our citizens," he said. "This commitment of freedom, however, does not require the redefinition of one of our most basic social institutions."

At the end of his remarks, Mr. Bush spoke of the need for tolerance, saying there was "no contradiction" between a government that respected every person but also protected the institution of marriage.

Neither Mr. Bush nor White House officials defined what they viewed as the difference between gay marriages and civil unions, which would extend legal rights to gay partners. But in supporting the rights of states to offer civil unions, Mr. Bush opened himself up to criticism from some of his most conservative supporters.

"We are concerned that he left the door open for the states to create gay marriage by another name, namely civil unions or domestic partnerships," said Robert Knight, the director of the Culture and Family Institute. "He started out great, but at the end he basically gave a green light to cities and states to create gay marriage by another name."

Gay supporters of Mr. Bush were also unhappy, some saying he was pandering to extreme conservatives.

"This is reminiscent of Pat Buchanan's culture-war speech at the 1992 Republican convention that helped lose the election for the first President Bush," said Patrick Guerriero, the executive director of the Log Cabin Republicans, a group of gay conservatives.

Mr. Guerriero said his group would attend the Republican convention in "record numbers" to defend "part of the American family" if the party chose to marginalize it.

Mary Cheney, a Bush campaign official and the openly gay daughter of Vice President Dick Cheney, had no comment on the announcement. Neither did Mr. Cheney.

Last month, in interviews with The Rocky Mountain News and Denver Post, Mr. Cheney said he would support the president on the issue.

"At this stage, obviously, the president is going to have to make a decision in terms of what administration policy is on this particular provision," he said, "and I will support whatever decision he makes."

White House officials struggled to cite examples of how allowing gay marriage would undermine the social fabric of the United States, as Mr. Bush suggested in his remarks.

Scott McClellan, the White House press secretary, said Mr. Bush addressed that question when he said that "ages of experience have taught humanity that the commitment of a husband and wife to love and to serve one another promotes the welfare of children and the stability of society."