The Japanese currency weakened to the 158-yen range against the dollar in New York on Friday, a level not seen since May 1990, after the Bank of Japan decided to leave monetary policy unchanged.
The BOJ's decision and comments Governor Ueda Kazuo subsequently made at a news conference led to speculation that the central bank will not be raising interest rates in the near future.
Market watchers believe the interest-rate gap between the United States and Japan is likely to remain for the time being, prompting a move to the higher-yielding dollar.