The yen weakened into the low 156-per-dollar range despite expectations that the Bank of Japan will raise its benchmark rate from 1.0% to 1.25% on Sept. 18, the highest level in 31 years. The currency had earlier strengthened into the 152s on expectations of a BOJ increase but lost about 4 yen in 10 days. The reversal followed the Federal Reserve's first interest-rate increase in three years and two months and its signal that further tightening remained possible, reinforcing expectations that the U.S.-Japan rate gap will stay wide. Even a 25-basis-point increase, equal to one-quarter of a percentage point, may not narrow the gap if U.S. rates rise at a similar or faster pace. Eight of 10 foreign-exchange specialists surveyed in Japan expect the yen to weaken again by year-end, citing the rate gap, higher global oil prices and Japan's worsening trade balance. Rising oil prices increase Japan's import bill because it relies heavily on crude imports, adding pressure to sell the yen and potentially encouraging further BOJ rate increases. The won also weakened, with the won-dollar exchange rate reaching 1,382.2 and rising nearly 40 won over three trading sessions.