The dollar was last up 0.1 percent against a basket of major currencies after hitting a peak of 99.99, its highest in four weeks. A stronger dollar tends to hurt profits for US multinationals. US crude oil prices edged higher, but their sharp decline since last year has weighed on energy companies' results.
Corporate earnings kick into high gear this week. Estimates for first-quarter S&P 500 results have fallen sharply since Jan. 1, with earnings for the period expected to have declined 2.9 percent from a year ago, Thomson Reuters data showed.
"There is some trepidation about what the earnings announcements are going to look like, and so investors are cautious," said John Carey, portfolio manager at Pioneer Investment Management in Boston. "Most people are thinking earnings are going to be weak due the strong dollar, lower oil prices and sluggish consumer spending due to the winter weather. But we'll see."
Among the companies expected to report this week are GE, Intel Corp and Johnson & Johnson, whose shares fell 1.5 percent to $100.55 on Monday. Several big banks, including JPMorgan Chase & Co and Bank of America Corp , also are due to report.
The Dow Jones industrial average fell 80.61 points, or 0.45 percent, to 17,977.04; the S&P 500 dropped 9.63 points, or 0.46 percent, to 2,092.43, and the Nasdaq Composite eased 7.73 points, or 0.15 percent, to 4,988.25.
The Nasdaq briefly traded above 5,000, within 110 points of its all-time intraday high.
In post-market trading, shares of Norfolk Southern Corp fell 3.8 percent to $100.94 after the railroad gave a disappointing outlook.
During the regular session, Apple Inc shares dipped 0.2 percent to $126.85, reversing earlier gains that followed reports the company may have received about an initial million orders for its Apple Watch.
Netflix Inc shares rose 4.4 percent at $474.68. The video streaming company said Friday it was seeking to increase its share authorisation by nearly 30 times as a possible first step toward a stock split.
NYSE decliners outnumbered advancers 1,902 to 1,144, for a 1.66-to-1 ratio; on the Nasdaq, 1,408 issues fell and 1,309 advanced, for a 1.08-to-1 ratio.
The S&P 500 posted twenty-four 52-week highs and no new lows; the Nasdaq Composite recorded 104 new highs and 24 new lows.
About 5.4 billion shares changed hands on US exchanges, below the 6 billion daily average for the last five sessions, according to BATS Global Markets.