In 2010, the United States filed a complaint alleging China was restricting foreign companies' transactions in foreign currencies by requiring them to use a network run by China UnionPay with renminbi-oriented transactions.
Every transaction from retail stores to automatic teller machines based in China's currency needed to be run through CUP, the United States said.
On Monday, the WTO "concluded that China maintains CUP as a monopoly supplier for the clearing of certain types of renminbi denominated payment card transactions."
Speaking on Air Force One, White House press secretary Jay Carney said the WTO "is announcing another clear win for the United States in a trade dispute with China."
"Today's win highlights that tackling unfair Chinese trade practices has been a priority of this president. This is another judgment in the United States' favor," Carney said.