By Mary Wisniewski
CHICAGO (Reuters) - Visa Inc said on Wednesday it is joining MasterCard Inc and American Express Co in barring its credit cards from being used to pay for ads on Backpage.com following a request from a Chicago sheriff who said the site is used by sex traffickers.
Cook County Sheriff Thomas Dart said that "escort" ads on Backpage.com and similar classified advertising sites make up the foundation of a sex-trafficking industry that preys on the young and vulnerable.
Earlier this week, he asked both Visa and MasterCard to cut off any association with the Backpage.com "adult" section.
"Visa's rules prohibit our network from being used for illegal activity," spokesman John Earnhardt said in a statement on Wednesday. "Visa has a long history of working with law enforcement to safeguard the integrity of the payment system and we will continue to do so."
MasterCard spokesman Seth Eisen said on Tuesday the company agreed to stop allowing the card to be used on Backpage. American Express had previously disallowed the use of its card for adult ads on the site, said spokeswoman Sanette Chao.
This leaves only Bitcoin, an electronic currency, to pay for Backpage adult ads, which Dart said will make placing the ads much more difficult.
"We have no naive notion that we'll end prostitution, end trafficking, end exploitation of children," Dart said. "What we've wanted all along is to make it more difficult and make (traffickers) easier to catch."
Liz McDougall, Backpage's general counsel, said in an e-mail on Tuesday the company had no comment. She could not be reached on Wednesday.
Backpage offers forums to find roommates and sell goods, like other classified advertising sites, but its primary revenue stream is through its adult page, according to Dart's office.
Cook County Sheriff's police have made more than 800 arrests since 2009 stemming from Backpage ads, Dart's office said.
"We commend these credit card companies for making it more challenging for traffickers to profit off of the exploitation of people," said Bradley Myles, CEO of Polaris, a Washington-based anti-trafficking group.
(Reporting by Mary Wisniewski; Editing by Will Dunham)