The U.S. Treasury Department said Wednesday no major U.S. trading partners were manipulating their currencies, but it said China's yuan remained undervalued despite Beijing's efforts to allow the currency to appreciate. “Treasury did not find that any major trading partner had manipulated its exchange rate for the purposes of preventing effective balance of payments adjustment or to gain unfair competitive advantage,” Treasury Secretary Timothy Geithner said as his department released its bi-annual report to Congress on global currency policies. China, which has been accused by U.S. lawmakers of artificially weakening the yuan to increase its exports, has made progress in making its currency more flexible, the Treasury report said. “China has taken steps to enhance exchange-rate flexibility,” Geithner said. “Even so, Treasury remains of the new that the [yuan] is undervalued.”