The International Monetary Fund has cut its outlook for U.S. economic growth amid uncertainties about President Donald Trump's economic policies.

The IMF's updated forecast says the world's largest economy will expand at a 2.1 percent annual rate this year. That is better than last year, but less than the IMF previously predicted and less than the three percent growth rate promised by Trump during his campaign for president.

The IMF said its previous outlook for improved growth was based on Trump's promises to slash taxes and regulation and boost spending on infrastructure to help economic expansion. But the global lender's experts now say they were able to learn too few details of these policies in discussions with U.S. officials.

An IMF assessment says the American economy is struggling to adapt to low productivity growth, technological changes that are reshaping the labor market, and an aging population. These economic changes mean that half of U.S. households have lower incomes now than they did in 2000, and the economy is not doing enough to spread income growth.

The global lender also says U.S. job growth is strong and the overall economy is now 12 percent larger than it was before the recession.