WASHINGTON, Dec. 21 (Xinhua) -- The tax cut bill approved by Congress Wednesday would only lift the U.S. economy modestly in 2018 and 2019, economists with J.P. Morgan said Thursday.

The U.S. Congress on Wednesday finally passed the Republican bill to overhaul the U.S. tax code over three decades, reducing income tax rates for companies and most families.

According to J.P. Morgan economists, the bill would add a 0.3 percent point to the U.S. gross domestic product (GDP) in 2018 and a 0.2 percent point to the GDP in 2019, as lower tax rates would boost private consumption and business investments.

The U.S. economy expanded at an annual rate of 3.2 percent in the third quarter of the year, according to the revised data released on Thursday by the Commerce Department.

While the tax bill would only slightly boost the economy, it would very likely swell the deficits of the U.S. federal government.

The Committee for a Responsible Federal Budget (CRFB), a bipartisan public policy organization based in Washington, said in a recent analysis that the tax bill could cost about 2 to 2.2 trillion U.S. dollars in the next decade, pushing up U.S. public debt to between 98 percent and 100 percent of GDP by 2027.