The yen gained momentum against the dollar on Wednesday as traders evaluated the Bank of Japan's monetary policy, while the dollar scarcely moved as investors ignored Fitch's downgrading of the U.S. credit rating.

The United States was downgraded by rating agency Fitch on Tuesday from AAA to AA+, a decision that startled markets and drew a rebuke from the White House despite the debt ceiling problem being resolved two months prior.

It noted projected fiscal decline over the following three years as well as ongoing, last-minute debt ceiling talks that put the government's ability to pay its obligations in jeopardy.

The dollar index that gauges the greenback versus its major pairs, climbed by 0.18% to 102.18, almost missing Tuesday's three-week high of 102.43.

EUR/USD muted at $1.098.

GBP/USD edged up by 0.12% at $1.279. On Thursday, BOE will determine interest rates, and the market is unsure whether they will rise from the current 5% level by 25 or 50 basis points.

USD/JPY ticked up by 0.55% to 142.53 per dollar and seemed ready to turn around three sessions of losses, with traders still evaluating the effects of the Bank of Japan's (BOJ) decision to relax its hold on interest rates on Friday.