The U.S. dollar fell to a seven-month low against the yen and near-record lows compared to the euro on Monday.
Analysts say the huge gap between what the United States buys abroad and what it sells hurts the dollar's value. The U.S. budget deficit also contributes to the dollar's decline.
On a visit to Ireland, U.S. Treasury Secretary John Snow said Washington supports a "strong dollar" but said the value is best set by open markets. He was re-stating long-standing administration policy.
Economists say a weaker dollar makes goods exported from the United States less expensive and more attractive on foreign markets.
Some information for this report provided by AFP and AP.