Watch VideoPlay Video
The yen rose again to a 15-year high against dollar on Tuesday, to 84.72. Traders are looking to test Japan's resolve to intervene, after the central bank failed to scare investors from betting on it rising further.
As mounting U.S. economic worries keep investors away from risk assets, the market is likely to push up the low-yielding yen. Traders say Japanese intervention will be a unilateral action, because the US isn't willing to boost its own currency in light of economic weakness.
Japanese authorities are expected to buy the dollar against the yen to curb the yen's strength if the dollar slides 3 or 4 yen in a single day.