California's Supreme Court has told San Francisco officials to stop same-sex marriages. The court will take up the issue again in May or June.

The ruling is a victory for conservative groups which have fought to block the city from officially sanctioning gay and lesbian unions. Over the past month, San Francisco authorities have issued marriage licenses to more than 3,700 same-sex couples.

The city has attracted gay and lesbian partners from around the United States since February 12, when Mayor Gavin Newsom enacted the controversial policy. The action went against state law, but Mr. Newsom said it is backed by the equal-rights provision of the California constitution.

The state attorney general asked the California Supreme Court to take up the case. The court, while it halted the marriages, did not rule on their legality. Governor Arnold Schwarzenegger says he opposes same-sex marriage because it violates state law, but has said he may support it if the law is changed.

On the other side of the country, Massachusetts lawmakers are debating a possible ban on same-sex marriages, two months before the unions are to be legalized in the state, under an earlier court ruling on the East Coast.

Communities in New York State, Oregon and New Mexico has followed the lead of San Francisco in challenging laws limiting marriage to heterosexual couples.

The gay marriage controversy has become part of the political debate in the United States in this election year. President Bush has stated his support for changing the federal constitution to define marriage as between a man and woman. Democratic challenger John Kerry also opposes gay marriage, but supports stronger legal rights for gay and lesbian partners.