The U.S. dollar fell to another 15-year low against the Japanese yen on Tuesday.
"The dollar was sold as investors tried to avoid risk," said Yuji Kameoka, chief currency strategist at Daiwa Institute of Research in Tokyo.
The yen's rise hurts the Japan's exporters by eroding their foreign-earned income when it is repatriated to Japan.
"We will take a decisive action, including intervention, when needed," Finance Minister Yoshihiko Noda said. "We will keep watching the currency market movement with grave concerns and closest attention."
Meanwhile, the greenback also fell to a new low against China's Yuan. China is focused on keeping its currency at a level that helps its own economy.
However, Chinese leaders have often criticized Washington for spending too much money - a move which will hurt the value of the dollar in the long run.