By David LawderWASHINGTON (Reuters) -The U.S. Treasury on Thursday said no major trading partner appeared to have manipulated its currency last year, but it added Japan to a foreign exchange "monitoring list," alongside China, Vietnam, Taiwan, Malaysia, Singapore and Germany, which were on the previous list.The Treasury's semi-annual currency report found that none of the countries examined met all three criteria triggering "enhanced analysis" of their foreign exchange practices during the four quarters through December 2023.Countries are automatically added to the list if they meet two of the three criteria: a trade surplus with the U.S. of at least $15 billion, a global account surplus above 3% of GDP and persistent one-way net foreign exchange purchases of at least 2% of GDP over 12 months.The Treasury said Japan, Taiwan, Vietnam and Germany all met the criteria for trade surpluses and an outsized current account surplus.Singapore met the criteria for engaging in persistent foreign exchange intervention and a material current account surplus, and Malaysia only met the current account surplus criteria, but once on the list, it takes two currency report cycles to be dropped off.China was kept on the monitoring list because of its large trade surplus with the U.S. and because of a lack of transparency surrounding its foreign exchange policies."China’s failure to publish foreign exchange (FX) intervention and broader lack of transparency around key features of its exchange rate mechanism continues to make it an outlier among major economies and warrants Treasury's close monitoring," the Treasury said in the report.