The S&P 500 stock index and the tech-heavy Nasdaq composite each lost 1.2%, with the S&P 500 closing at 2,882 and the Nasdaq closing at 7,863.
Those higher prices pulled down the yield on the 10-year Treasury bond to 1.65% from 1.73% late Friday.
Technology, health care and consumer discretionary stocks accounted for much of the market's decline.
The Labor Department will release its consumer price index for July on Tuesday and the Commerce Department will release last month's retail sales results on Thursday.
Anxiety and fear over the U.S.-China trade war continues to hover over the market and has taken stocks on a wild ride in August.
The indexes are down more than 3% for the month, but still up solidly this year, led by the Nasdaq's 18.5% gain.
Trump has said he'd be "fine" if the U.S. and China don't go ahead with a meeting next month, dampening investors' hopes for a path to resolving the economically damaging trade war.