It’s the latest approach to fighting online child pornography: Cut off online payment mechanisms for Web sites selling the material.

That’s the mission of the new Financial Coalition Against Child Pornography, a group of banks, credit card and Internet companies that have teamed up to fight what was recently described in Congress as a $20 billion industry that continues to expand in the United States and overseas. The idea behind the new group, formed last month, is to cut off the mechanisms Web sites use for receiving payment for child pornography. European banks are expected to join in the next few months.