The yen retreated from the strongest in four weeks against the dollar before the Federal Reserve concludes a two-day policy meeting today.

The yen has been the biggest gainer among the 10-currency Bloomberg Correlation-Weighted Indexes in the past week as tumbling oil added to concern the global economy will falter, boosting demand for havens. The ruble collapsed to a record yesterday even after Russia increased borrowing costs to the most since 1998. A gauge of emerging-market currencies fell to a 12-year low. New Zealands kiwi declined after the South Pacific nations current-account deficit widened.

The yen dropped 0.5 percent to 116.98 per dollar at 9:26 a.m. in Tokyo from yesterday, when it touched 115.57, the strongest since Nov. 17. Japans currency slid 0.4 percent to 146.27 per euro after advancing 1.6 percent in the previous two sessions. The dollar was little changed at $1.2503 per euro.

New Zealands kiwi fell 0.2 percent to 77.82 U.S. cents.