The yen fell to a 39-year low past 162 against the dollar on Tuesday in Tokyo.
The Japanese currency reached the lower 162 zone, its weakest level since December 1986. The drop occurred amid expectations of Federal Reserve interest rate hikes this year.
Japanese Finance Minister Satsuki Katayama said the government is "always" ready to act if needed. Markets showed little reaction to the warning.
Masahiro Ichikawa of Sumitomo Mitsui DS Asset Management noted that further acceleration in the yen's decline would raise the chance of intervention. Tokyo stocks rose, with the Nikkei gaining 594.21 points to close at 70,062.32.