The International Monetary Fund (IMF) said the US economic recovery was gathering steam but remained uneven.
It also said the Federal Reserve had more room to cut interest rates if deflation risks persist.
Consumer sentiment has improved with the end of the Iraq war and demand should rise with tax cuts, the rise in stock prices, low interest rates and falling oil prices, the fund said.
But it expressed concern about the erosion in the US government budget position, due in part to the latest tax cuts. It said mounting deficits could make coping with the financial needs of the ageing baby-boom generation tough and risked crowding out investment and hurting productivity growth.
The fund said "decisive" fiscal action was needed.
The IMF projected US gross domestic product growth of around 2.25 per cent in 2003 and 3.5 per cent in 2004.
The Federal Reserve won praise for a "strong and proactive" response to the US economic woes. The IMF said it welcomed the central bank's willingness to consider alternative policy tools should they be needed to forestall deflation.
Short-term interest rates stand at a 45-year low after 13 cuts since the beginning of 2001.
When fears over possible deflation emerged earlier this year, Fed officials took pains to reassure markets they could use alternative measures, such as buying longer-term Treasury bonds, to shore up growth if needed.
However, with recent signs of improvement in the economy, concerns over falling prices have waned. Although the US economy clambered out of a mild recession in 2001, growth has been slow to accelerate.
The deficit in the US current account, the broadest measure of trade, has swelled to around 5 per cent of gross domestic product. However, the fund said the dollar's recent slide may help narrow the gap to more sustainable levels.
The IMF urged the US to contain spending growth and review tax priorities, given the uncertain outlook for future tax revenues. Some IMF directors suggested energy-related taxes to help bolster the fiscal position.