Beijing said on Tuesday it had "reservations" over a WTO ruling largely backing the United States in a dispute over lucrative electronic payments, in which US companies are global leaders but lag in China.
More than $1 trillion in electronic payment services (EPS) transactions, including both debit and credit cards, are processed each year in China, the world's second largest economy.
Washington had gone to the World Trade Organization to accuse Beijing of discriminating against US credit card firms.
Ministry of Commerce spokesman Shen Danyang said in a statement that while not all aspects of the WTO ruling went against China, the government had some "reservations" and "will seriously review the panel's report".
The WTO, he said, had found that EPS came under the payment and money transmission services that China "promised to open up at its entry into the WTO".
"China has reservations on this," he added.
Both sides have 60 days to appeal the WTO decision. The Office of the US Trade Representative said it planned to accept the report.
The WTO announced Monday in Geneva that Beijing had violated trade rules in regulations that entrenched China Union Pay, or CUP, as the dominating force in the market.
Among the violations cited were Beijing's requirement that all payment cards issued in China bear the CUP logo, and all terminal equipment must be capable of accepting CUP-logo cards.
Washington claimed China excluded foreign companies from the market for EPS payments denominated in Chinese yuan, only allowing non-Chinese WTO members to supply facilities for card payments in foreign currency.
But the WTO rejected US accusations that China maintains CUP as an "across the board monopoly supplier" for processing all payment card transactions in renminbi, as the yuan currency is officially known.
The WTO nonetheless determined that CUP was a monopoly supplier for clearing certain types of yuan payment-card transactions.