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President Bush, reacting to a new Massachusetts state court ruling, says a constitutional amendment will be necessary to ban gay marriages (search) if judges persist in approving them.

In a written statement late Wednesday, Bush termed "deeply troubling" the decision that same-sex couples in Massachusetts have a right to marry — not just form civil unions — and reiterated a position staked out in his State of the Union (search) speech last month.

"Marriage is a sacred institution between a man and a woman," he said in the statement. "If activist judges insist on redefining marriage by court order, the only alternative will be the constitutional process. We must do what is legally necessary to defend the sanctity of marriage."

The Massachusetts Supreme Court's (search) advisory opinion that gays are entitled to nothing less than marriage set the stage for the nation's fi1rst legally sanctioned same-sex weddings by the spring.

The issue has the potential to become a hot factor in the presidential campaign.

Massachusetts Sen. John Kerry, the front-runner for the Democratic presidential nomination, said in his own statement: "I believe and have fought for the principle that we should protect the fundamental rights of gay and lesbian couples — from inheritance to health benefits. I believe the right answer is civil unions. I oppose gay marriage and disagree with the Massachusetts Court's decision."

Retired Gen. Wesley Clark, another Democratic presidential candidate, said: "I leave that to the states and the courts — whether you call it a marriage or not, I leave up to the states and churches and synagogues and mosques."

Bush's statement was similar to his remarks in his Jan. 20 State of the Union address in which he said that if judges "insist on forcing their arbitrary will upon the people, the only alternative left to the people would be the constitutional process."

Conservative activists and religious groups, banding together under the name the Arlington Group, gathered in Washington this week to plot strategy. Some participants said they left with a White House commitment to fight for a constitutional amendment.

"We were given direct assurances from the very top," said Kelly Shackelford, president of the Texas-based Free Market Foundation. "There's no doubt. It's our understanding that the president is waiting for a day when there is not a massive news story to do it himself."

Another group, the Alliance Defense Fund based in Scottsdale, Ariz., sent out an e-mail asserting, "This morning, President Bush agreed to join the effort to push for the passage of this amendment."

Tony Perkins, president of the Family Research Council, a leading group of social conservatives, said, "I would not be surprised at all to see the president come out very soon calling on Congress to act." He said he could not speak for Bush but that "it appears that things are falling in line for that to happen."

Grover Norquist, president of Americans for Tax Reform and a conservative who is close to the White House, said a constitutional amendment "is what you'd expect the president to do. ... They are forcing the president's hand — if you say only an amendment can fix this, guess what, you're going to get an amendment."

White House press secretary Scott McClellan said the administration would review the Massachusetts' opinion.

Recalling Bush's remarks in his State of the Union speech, McClellan said, "What he said at that time, that if judges continue to force their arbitrary will upon the people, that the only alternative to the people would be a constitutional process. And that remains his view."