MoveOn.org, a liberal political group, said Thursday it has launched a petition drive that calls on America Online Inc. to halt plans to launch a paid certified email service that would bypass spam filters and deliver messages directly to subscribers.

The online petition was emailed to all 3 million MoveOn.org members on Wednesday, Adam Green, spokesman for the political group's Civic Action unit, said. MoveOn.org members who subscribe to AOL, a division of Time Warner Inc, were sent the petition last week.

The group has gathered more than 200,000 signatures, Green said.

MoveOn.org plans to hold a news conference on Tuesday to unveil a number of organizations that have joined it in opposing AOL's pay-to-send system, Green said. Those groups include political organizations from the left and the right, nonprofits, businesses and Internet advocacy groups. Among the Internet entrepreneurs who have joined the petition drive is Craig Newmark, founder of the popular CraigsList online classifieds service, Green said.

MoveOn.org claims AOL's certified email program, which it plans to launch this quarter, would eventually lead to slower delivery and inferior service for charities, small businesses, civic organizations and individuals who can't afford to pay for sending bulk email.

In addition, offering guaranteed delivery only to paying email senders destroys the Internet as a neutral platform in which everyone is treated equally, a practice that has enabled Internet startups to compete with larger established firms, MoveOn.org said.

"The Internet only thrives if it's free to everybody, and everybody is equal on it," Green said. "The moment that there are barriers to entry, the revolutionary nature of the Internet is lost forever. Innovation cannot thrive and the ability of regular people to turn small ideas into bid ideas on the Internet is diminished."

AOL, which has 26 million subscribers, said MoveOn.org was wrong in saying that email services for nonpaying senders would degrade. The two organizations had met before the start of the petition drive, but failed to reach an agreement.

"We don't mind when organizations make philosophical and political arguments, as long as they have the correct facts," AOL spokesman Nicholas Graham said. "After having a conversation with them, it was pretty clear they weren't interested in providing their members with accurate information or the truth."