Goldman Sachs believes the U.S. economy will slow significantly in the second half of next year as the Federal Reserve continues to raise interest rates and the effects of the tax cut fade.

"Growth is likely to slow significantly next year, from a recent pace of 3.5 percent-plus to roughly our 1.75 percent estimate of potential by end-2019," wrote Jan Hatzius, chief economist for the investment bank, in a note to clients on Sunday. "We expect tighter financial conditions and a fading fiscal stimulus to be the key drivers of the deceleration."

The bank sees the economy expanding at 2.5 percent in the fourth quarter of this year, down from 3.5 percent last quarter. Real GDP growth will come in at 2.5 percent again in the first quarter of 2019, but then will slow to 2.2 percent, 1.8 percent and 1.6 percent in the next three quarters, respectively.