The U.S. dollar index fell 4.1 percent versus six other currencies in 2009 though it rebound about 4 percent in December and wrapped up the year with 77.87 points.

The dollar index, a measure of the greenback against a trade-weighted basket of major rivals, traded at 77.87 on December 31.

A dollar rally in recent weeks has seen the index post a 3.6% December rise, but the gauge remains on track for a 4.5 percent loss.

The dollar is on pace to gain versus the Japanese yen this year, by 1.9%, helped by the strong 7.1% improvement this month.

The dollar rallied as investors looked for signs a recovery is taking hold. Some traders have moved to safer assets like the dollar to look in profits after a strong 2009.