SACRAMENTO, Calif. (Legal Newsline)--Attorney General Jerry Brown and Gov. Arnold Schwarzenegger are asking Internet service providers to block access to child porn Web sites and newsgroups, and to clear their servers of existing child porn.

"Protecting the safety of our children must be a top priority, not just for government, but also for businesses with the direct power to reduce the ability to conduct illegal activity," Brown and Schwarzenegger wrote in a joint letter to the California Internet Service Provider Association, which represents more than 100 Internet service providers in California.

Three telecom networks--Verizon, Time Warner and Sprint--have already started blocking Web addresses of known child porn sites. Brown and the governor praised the companies and called on others to follow suit.

"It is not enough, however, for only a few Internet service providers to join the fight against online predators," the letter said. "Child pornography is not protected by the First Amendment, and distributing this material is illegal."

Jon Davies, a spokesman for Verizon, told Legal Newsline his company blocks access to a list of sites and news groups provided by the National Center for Missing and Exploited Children.

The New York0based company isn't involved in drawing up the list.

"We don't verify the list," Davies said. "We trust them to verify it."

Davies said Verizon has no interest in monitoring what its customers do online, but added that posting, storing or sharing child porn violates Verizon's terms of service.

"We're not going to be the Internet police looking at web usage," he said. "We're a Strong proponent of free speech, and we continue to do this, but in this case, we're deferring to NCMEC's opinion."

Calls to the California Internet Service Providers Association were not returned Friday.

Brown and Schwarzenegger closed their letter by asking for a "positive response" within 10 days.