NEW YORK — Faced with opposition from conservative groups and some pornography Web sites, the Internet's key oversight agency voted yesterday to reject a proposal to create a red-light district on the Internet.

The decision from the Internet Corporation for Assigned Names and Numbers reversed its preliminary approval last June to create a ".xxx" domain name for voluntary use by the adult entertainment industry.

Paul Twomey, ICANN'S chief executive, said the decision largely came down to whether by creating an "xxx" domain ICANN might be put in a position of having to enforce all of the world's laws governing pornography.

ICANN had postponed making a final decision in August after the U.S. government underscored objections it had received.

ICANN's rejection in a 9-5 vote ends, for now, a six-year effort by ICM Registry Inc. of Jupiter, Fla., to establish a domain for the porn industry. ICANN first tabled its bid in 2000 out of fear it would be getting into content control.

ICM resubmitted its bid in 2004, this time structuring it with a policy-setting organization to free ICANN of that task.

The company argued the domain would help the $12 billion online porn industry clean up its act. Those using the domain would have to abide by yet-to-be-written rules designed to bar such trickery as spamming and malicious scripts.

Anti-porn advocates, however, say that such a domain name would only legitimize adult sites.

Many porn sites also objected, fearing that such a domain would pave the way for governments — the U.S. or repressive regimes abroad — to filter speech that is protected here under the First Amendment.

Democratic Sens. Max Baucus of Montana and Mark Pryor of Arkansas have introduced legislation that would create a mandatory ".xxx."