The majority of internet service providers in the US have signed a pact to ban child pornography from being viewed online.

All cable providers in the National Cable & Telecommunications Association (NCTA) have vowed to block sites listed as carrying child pornography held by the National Center for Missing and Exploited Children (NCMEC).

"We are deeply grateful for this industry-wide attack on child pornography," said Ernie Allen, president of NCMEC.

"It is not possible to arrest and prosecute every offender. We must be creative and build new public-private partnerships to address this insidious problem more effectively. Today's announcement represents a bold step forward."

The pact also means that servers hosting such material cannot be owned or run by the companies and they can report instances where that is happening to the authorities.

"NCMEC has signed similar agreements with individual companies, but this agreement is the first NCMEC has reached with an entire sector of the nation's communications industry," said Rhode Island Attorney General Patrick Lynch.

"The agreement will limit the ability of predators to store and exchange images of exploitation of those who are among the more vulnerable in society. We congratulate the cable industry for taking a stand in support of child safety."

The ISPs are also looking at ways to extend the elimination of such material on other mediums, such as news groups.

"Building on our strong commitment to online safety, the cable industry wants to help combat child pornography and exploitation," said Kyle McSlarrow, president of the NCTA.

"By signing the memorandum, cable ISPs are reaffirming their strong commitment to online safety and internet literacy for all American families."