The U.S. Treasury Department said Friday that Japan remains on a list of countries it monitors over potentially "unfair" currency practices, while noting that foreign exchange intervention should only take place in "very exceptional" cases amid the rapid weakening of the yen against the U.S. dollar.

In a semiannual report to Congress on currency manipulation, the department named 12 economies on its "monitoring list" — China, Japan, South Korea, Germany, Italy, India, Malaysia, Singapore, Thailand, Taiwan, Vietnam and Mexico. All except Taiwan and Vietnam were on the list in a December 2021 report.

The department assesses whether a country has manipulated its currency exchange rates to gain an unfair trade advantage through three criteria — the size of trade surplus with the United States, the size of current account surplus as a share of gross domestic product, and the extent of intervention in foreign exchange markets.