The value of U.S. sovereign debt declined on recent rises in U.S. long-term interest rates, more than offsetting an increase in the value of euro-denominated assets due to the appreciation of the single European currency, the ministry said.
The reserves mainly consist of securities and deposits denominated in foreign currencies and gold, as well as reserve positions and special drawing rights Japan holds at the International Monetary Fund.
The Finance Ministry also said that in January it purchased €400 million of debt issued by the European Stability Mechanism, a permanent rescue fund for the 17-nation eurozone designed to provide money to stricken governments.