NEW YORK, July 29 (Reuters) - Internet service providers

(ISPs)

Comcast Corp and United Online Inc's NetZero have agreed to block access to child pornography, the New York Attorney General's office said on Tuesday.

The announcement comes a week after New York Attorney General Andrew Cuomo threatened to pursue legal action against Comcast Cable Communications LLC if it did not agree to reforms. Several other ISPs, such as Verizon Communications Inc and Sprint Nextel Corp agreed in June to block Internet bulletin boards and websites nationwide that disseminate child porn.

"I commend the companies for working with my office to aggressively eradicate online child pornography and strongly urge all outstanding Internet service providers across New York and the nation to get on board," Cuomo said in a statement.

Other major ISPs that have signed on with Cuomo's initiatives include Time Warner Inc's AOL unit, AT&T Inc and Time Warner Cable Inc.

The companies have agreed to completely block access to all child porn newsgroups and said they will purge their servers of all child pornography websites identified by the National Center for Missing & Exploited Children.

Representatives for Comcast and United Online were not immediately available for comment.