It said a many economies have conducted foreign exchange market intervention in one-sided manner.
The United States on Friday placed 11 countries, including India, China, Japan, South Korea, Germany and Italy in the currency practices monitoring list.
Other countries named by the Department of Treasury in its quarterly report to Congress, the first under the Biden administration, are Ireland, Malaysia, Singapore, Thailand and Mexico.
All except Ireland and Mexico were covered in the December 2020 report, which was under the previous Trump administration.
As directed by Congress, Treasury has established a monitoring list of major trading partners that merit close attention to their currency practices and macroeconomic policies.
An economy meeting two of the three criteria in the 2015 Act is placed on the Monitoring List.
These are a persistent, one-sided intervention in the foreign exchange market that occur when net purchases of foreign currency are conducted repeatedly, in at least six out of 12 months, and these net purchases total at least two per cent of an economy's Gross Domestic Product (GDP) over a 12-month period.
As a further measure, the Treasury will add and retain on the Monitoring List any major US trading partner that accounts for a large and disproportionate share of the overall US trade deficit even if that economy has not met two of the three criteria from the 2015 Act, it said.
In its report, the Treasury said that a number of economies have conducted foreign exchange market intervention in a persistent, one-sided manner.
"Over the four quarters through December 2020, five major US trading partners -- Vietnam, Switzerland, Taiwan, India and Singapore -- intervened in the foreign exchange market in a sustained, asymmetric manner with the effect of weakening their currencies," it alleged.
Three of these economies -- Vietnam, Switzerland, and Taiwan -- exceeded the two other thresholds established by Treasury to identify potentially unfair currency practices or excessive external imbalances, which could impede the US growth or harm US workers and firms, the report said.
According to the report, the Chinese economic growth in 2020 exceeded that of other large economies but has been driven by the early resumption of manufacturing and increased external demand, especially for medical supplies, personal protection equipment and electronics.
"Questions remain about the continued strength of the Chinese recovery absent a sustained increase in household consumption. While official data do not show significant accumulation of foreign exchange assets by the central bank, China's failure to publish foreign exchange intervention and broader lack of transparency around key features of its exchange rate mechanism and the activities of state-owned banks warrant close monitoring of renminbi developments going forward," it said.
Over the four quarters through December 2020, a number of economies have experienced significant expansions in their current account surpluses as the pandemic drastically affected global trade, including China, Taiwan and Singapore, while other economies, including Germany and Vietnam have maintained large current account surpluses, which allowed for external asset stock positions to widen further, it added.
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