California Governor Arnold Schwarzenegger has told his top legal official to act against the city of San Francisco for allowing gay marriages.
Gay couples are flocking to San Francisco
He ordered the state's attorney-general to take immediate steps to get a court ruling against the same-sex weddings.
Mr Schwarzenegger said they represented "an imminent risk to civil order".
More than 3,000 gay couples have been married in San Francisco since the city's new mayor decided to defy state law and allow such weddings.
On Friday, a judge denied a request by the conservative group, Campaign for California Families, for an injunction halting the same-sex marriages.
He said the group had failed to show convincing evidence that allowing gay weddings to continue would cause irreparable harm.
It was the second failed attempt to secure an injunction barring the unions.
'Rule of law'
Hours after Friday's court hearing, Mr Schwarzenegger wrote to the state's attorney general, Bill Lockyero.
"Our civilised society and legal system is based upon a
respect for and adherence to the rule of law,"
"The city and
county of San Francisco's unfortunate choice to disregard
state law and grant marriage certificates to gay couples
directly undermines this fundamental guarantee.
"Because the city and county of San Francisco's actions are
directly contrary to state law and present an imminent risk to civil
order, I hereby direct you to take immediate steps to obtain a
definitive judicial resolution of this controversy."
San Francisco's Mayor, Gavin Newsom, believes the state law requiring marriage to be the union of a man and a woman discriminates against gays and lesbians.
As well as issuing marriage licences, his officials are also suing the state in an attempt to the get the law overturned.
Gay couples hope more cities will follow San Francisco's lead
A spokesman for the mayor, reacting to
Mr Schwarzenegger's directive, said: "The truth is, thousands of people are involved in loving
relationships and having them recognised for the first
"We urge the governor to meet with
some of the couples because what's happening is both lawful
Gay men and lesbians have travelled from across the US to get married in San Francisco.
The BBC's David Willis in San Francisco says some regard what is happening in the city as a landmark moment in the struggle for gay rights and have likened it to the campaign against racial segregation in America.
Californians voted against gay and lesbian marriages under Proposition 22 in 2000, which says marriage is limited to one man and one woman.
Only the state of Vermont sanctions
civil unions between same-sex couples, while Massachusetts,
after a state High Court ruled that banning gay marriage
was unconstitutional, is set to become the first state to
approve same-sex marriage later this year.
On Friday, a county
in the western state of New Mexico briefly issue marriage licences
to dozens of gay couples.
"We were issuing licences today but we stopped because the state
attorney-general issued a statement," Sandoval County clerk's office
official Melinda Foster said.
New Mexico attorney-general Patricia Madrid declined to formally rule
on the issue, but issued an advisory letter stating that "no county clerk
should issue a marriage license to same-sex couples because those
licenses would be invalid under current law".