The Internet's key oversight agency has revived a proposal it earlier rejected to create an online red-light district, after adding stronger provisions to prohibit child pornography and require labeling of Web sites with sexually explicit materials.

The use of the proposed ".xxx" domain name would remain voluntary, but any porn sites that choose to use it instead of the more popular ".com" would be subject to the new terms issued late Friday by the Internet Corporation for Assigned Names and Numbers.

The idea of a separate ".xxx" domain has generated significant opposition from conservative groups and even some pornography Web sites.

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But ICANN officials said they initially rejected the proposal in May not because of the opposition but because of concerns that the agency might be put in a difficult position of having to enforce all of the world's laws governing pornography. They noted that various nations' speech-related laws sometimes conflict with one another.

The new proposal does not directly address any potential conflicts in laws, but it calls for the company backing it, ICM Registry Inc. of Jupiter, Florida, to hire independent organizations to monitor porn sites' compliance with the new rules.

ICANN, the agency in Marina del Rey, California, designated by the U.S. government to oversee domain name policies, opened the proposal to public comment but did not indicate when it would rule.

If approved, ICM would be required to help develop mechanisms for promoting child safety and preventing child pornography, "including practices that appeal to pedophiles or suggest the presence of child pornography on the site."

Porn sites would have to participate in a self-descriptive labeling system, likely one from the Internet Content Rating Association.

Under it, Web sites add tags based on such criteria as the presence of nudity and whether it is in an artistic or educational context, such as for sites on breast feeding.

Relatively few sites now participate, although major Web browsers have mechanisms for reading the tags.

ICM also would have to develop automated tools to check for compliance and give users ways to report violations.

ICM believes the domain would help the $12 billion online porn industry clean up its act, as those using it must abide by rules designed to bar such trickery as spamming and malicious scripts.

Anti-porn advocates, however, countered that sites would be free to keep their current ".com" address, in effect making porn more easily accessible by creating yet another channel to house it.

Many porn sites also objected, fearing that an ".xxx' domain would pave the way for governments or even private industry to filter speech that is protected in the United States by the First Amendment.