President George Bush backed a constitutional amendment banning gay marriage today, saying he wants to stop activist judges from changing the definition of the "most enduring human institution."
Marriage cannot be severed from its cultural and moral roots, Mr Bush said, urging Congress to approve such an amendment.
"After more than two centuries of American jurisprudence and millennia of human experience, a few judges and local authorities are presuming to change the most fundamental institution of civilisation," Mr Bush said in the White House.
"Their action has created confusion on an issue that requires clarity."
Presidential spokesman Mr Scott McClellan said in advance of Mr Bush's announcement that the president wanted to end "growing confusion" that has arisen from court decisions in Massachusetts, and San Francisco's permitting more than 3,000 same sex unions.
"The president believes it is important to have clarity," he said. "There is widespread support in this country for protecting and defending the sanctity of marriage."
Mr McClellan said Mr Bush believes that proposed legislation for such an amendment "meets his principles" in protecting the "sanctity of marriage" between men and women.
But Mr Bush did not specifically embrace any particular piece of legislation in his announcement.
Mr Bush decided to take action partly because the Massachusetts Supreme Judicial Court recently ruled that it is unconstitutional to bar gay couples from marriage. That decision could result in gay weddings there as early as May, Mr McClellan said. "We're two months away," he said.
Mr McClellan said 38 states have passed laws protecting the "sanctity of marriage and the president will call on Congress to move quickly to pass legislation that can then be sent to the states for ratification.
"We need to act now," he said. "The constitutional process will take time."