America has not changed its strong dollar policy despite weeks of sharp falls on the currency markets, Treasury spokesman Tony Fratto has said.
The dollar has hit a series of lows since early November
"Our policy is for a strong dollar and we believe currencies should be set in open and competitive markets," he told reporters.
The dollar has hit record lows since early November, amid speculation that Washington is allowing it to fall.
The movement has encouraged talk of concerted market intervention.
Mr Fratto also reiterated calls for China to makes its currency - currently pegged against the dollar - more flexible.
Some analysts have speculated that Beijing might allow the yuan to appreciate against the dollar, a theory that weighed heavily on markets last week.