An attempt to change the US constitution to ban gay marriage has been rejected by the Senate.
Some states and towns have gone ahead with gay weddings
The proposal, sponsored by Republicans and backed by President Bush, failed to gain the support of 60 senators it needed to progress to the next stage.
Republicans vowed to fight on, but the measure is now unlikely to be passed before the November elections.
Same-sex marriage has been thrown into the spotlight after some US states and towns moved to make it legal.
The proposal gained a slight majority of 50-48 - not enough to take the amendment to a formal vote.
But Republican senators said they would carry on with their attempt to make it law.
"I would argue that the future of our country hangs in
the balance because the future of marriage hangs in the
balance," said Senator Rick Santorum.
But the Democrats' leader in the Senate, Tom Daschle, said there was no "urgent need" to amend the constitution.
Republicans say they have been forced to take action after Massachusetts' highest court ruled gay couples could be legally wed, and the city of San Francisco started
issuing marriage certificates to gay partners.
There are 38 US states which have already banned homosexual marriage, but lawsuits in Florida, Nebraska, New Jersey and Oregon are seeking to have it ruled legal.
Mr Bush was hoping to make individual states' attempts to legalise it irrelevant, by outlawing it nationwide.
In his weekly radio address at the weekend, he called marriage between a man and a woman "the most
fundamental institution of civilisation".
"This difficult debate was forced upon our country by a few activist judges and local officials, who have taken it on themselves to change the meaning of marriage," he said.
"A constitutional amendment should never be undertaken lightly
- yet to defend marriage, our nation has no other choice."
His Democrat rival, Senator John Kerry, says that he and his running mate, John Edwards, think states should be allowed to look after the matter themselves.
"Both John and I believe firmly and absolutely that marriage is
between a man and a woman. But we also believe that you don't play
with the constitution of the United States for political purposes
and amend the Bill of Rights when you don't need to," he said.