The United States' economy is operating at or close to full capacity and its GDP growth is expected to reach 2.5 percent in 2018 and 2.3 percent in 2019, a UN report said Thursday.

Despite slightly moderated activity in the first quarter of 2018, prospects for the year remain firm, buoyed by major fiscal stimulus measures "introduced in the Tax Cuts and Jobs Act of December 2017 and Bipartisan Budget Act of 2018," said the newly updated UN World Economic Situation and Prospects (WESP) 2018.

While noting U.S. average income tax rates have dropped by 2 percentage points this year, the report pointed out the after-tax wage inequality is expected to continue to rise, as higher income households reap a greater share of tax cuts.

With regard to U.S. corporate tax reduction, WESP 2018 said a steep decline in the corporate tax rate will continue to support investment in the near term in the country.

On the Budget Act, the report said U.S. additional federal spending will amount to 1 percent of GDP in 2018-2019.

These stimulus measures will allow the U.S. federal deficit to widen from 3.5 percent of GDP in 2017 to about 5 percent by 2019, and government debt will continue to rise relative to GDP for the next decade, it said.

At the same time, WESP 2018 showed positive U.S. employment figures, saying the unemployment rate has dropped to 4.1 percent, below most estimates of its long-run equilibrium level.

It also said the ratio of job openings to job seekers in the United States is at its highest level since at least 2000, and that its rising capacity utilization rates have supported a rebound of investment in equipment.