The dollar weakened against a basket of currencies on Tuesday in advance of a Federal Reserve meeting where policymakers are expected to decide on the reduction of the central bank's $4.2 trillion worth of bond holdings.
The Fed's possible move to further roll back stimulus has not stemmed the greenback's weakness this year as other major central banks are considering steps to either slow their bond purchases or raise interest rates.
Analysts widely anticipate Fed policymakers to announce a lowering of monthly bond purchases starting in October when their two-day meeting ends on Wednesday. They expect Fed officials would leave the door open for a rate increase at their Dec. 12-13 meeting.
"It's just a restless market before the Fed," said Joe Manimbo, senior market analyst at Western Union Business Solutions in Washington.
The index that tracks the dollar against six currencies was down 0.27 percent at 91.80, which was not far from the over 2-½ year low of 91.011 set on Sept. 8.