The S&P 500 ended the day down 0.6% at 2,821.80, following declines on Thursday and Friday.
On Thursday, the benchmark S&E 500 index was down 0,638.07 points, or 0.4%, to 2,804.21.
On Friday, the Nasdaq Composite Index lost 0.9% to 4,521.24.
The Dow Jones Industrial Average was up 1.7% to 22,921.28.
The US economy is expected to grow by just 0.3% in the third quarter, which ends on March 16, according to a report from the Congressional Budget Office.
On Monday, the Trump administration said it would be cutting federal aid to countries that impose new trade restrictions on the US.