A new voluntary system aimed at rooting out online copyright piracy using a controversial "six strikes" system is set to be implemented by US Internet providers soon, with the impact unclear.

The program was created with the music and film industry and the largest Internet firms, with some prodding by US government.

The system had been set to take effect late last year but was delayed until early 2013 by the Center for Copyright Information, the entity created to manage the program.

Even though the program became known as "six strikes," backers say the name is misleading and that it is not aimed at cutting off Internet access for people downloading pirated films or music.

The center's director Jill Lesser said the program is not "punitive."

"We believe a voluntary, flexible program will be the best way to address this, and we think consumers will respond to it," she told AFP.

Participating in the program are the five largest broadband Internet providers -- Comcast, Time Warner Cable, AT&T, Cablevision and Verizon -- covering some 85 percent of US residential customers.

Lesser said the program should be launched "very soon" after some technical issues are worked out, but offered no date.

A Verizon document leaked on the TorrentFreak blog suggests that the big Internet provider would deliver warnings for the first two suspected offenses and for the third and fourth incident, redirect customers to a page where they would have to "acknowledge" the warning.

For the fifth and six offenses, Verizon would "throttle" the Internet download speeds of customers to just above dial-up speeds. Customers could appeal the actions by paying $35 for a review by an arbitrator.

Verizon spokesman Ed McFadden said the report was based on a "working draft document," and that the company is still developing its response.

Other leaked documents showed AT&T would block users' access to some of the most frequently-visited websites and that Time Warner Cable would temporarily interrupt the ability to browse the Internet, according to TorrentFreak.

Lesser said the program is not aimed at operators of public Wi-Fi networks such as cafes, though critics disagree.

"It's becoming clear that operating a public Internet hotspot is going to be nearly impossible" because of potential copyright violations on sites like YouTube and Facebook, said Cory Doctorow, editor at tech blog Boing Boing.

But Lesser insisted the program "will not shut down public wireless access."

Six strikes has received a mixed response, but even some Internet freedom activists say it is preferable to a government-mandated program like the Stop Online Piracy Act, which failed last year to win congressional approval.

The program could "play a useful and positive role in addressing the problem of copyright infringement without causing a lot of problems for consumers and the architecture of the Internet," said David Sohn of the Center for Democracy & Technology.

But Chris Soghoian of the American Civil Liberties Union said it was "biased" toward copyright holders.

"The rights holder doesn't have to pay to accuse you of anything. You have to pay to assert your innocence," said Soghoian, the principal technologist with the ACLU's Speech, Privacy and Technology Project.

He said similar programs in other countries have proven unpopular and failed in many cases to accomplish their stated goals.

"There is a proven way of reducing infringement, and that is to create things people want to buy at a reasonable price and make it easy to play it on any device they own," Soghoian said.

Derek Bambauer, a law professor at Arizona State University who has worked on an ACLU lawsuit seeking more information on the program, said it is unlikely to have a major impact on piracy.

The French HADOPI law produced well over a million claims of infringement but "very little follow-on," he noted.

Bambauer said the effort appears to be "backdoor policymaking" by the US administration after it failed to implement any new policy.

But the US system is not a government program and entities are participating voluntarily, Lesser said, adding that the effort sought to learn from other countries' programs.

In France, she said, merely announcing the program discouraged illegal file-sharing by "people who thought they were doing this anonymously," and drove an increase in legal services.

"We hope there will be a similar psychological impact here," Lesser added.