Investors sent stocks lower ahead of the release of corporate earnings that Wall Street will digest in coming weeks.
The Dow Jones industrial average lost 48 points, or 0.4%, to 13,336 shortly after the opening bell.
The broader Standard & Poor's 500 index lost seven points, or 0.5%, to 1,455. The Nasdaq was down nine points, or 0.3%, to 3,090.
Earnings season unofficially begins with aluminum giant Alcoa Inc., which is to release earnings after the markets close Tuesday.
Companies in the S&P 500 are expected to report average fourth-quarter earnings growth of 3.3%, according to S&P Capital IQ.
Though still positive, that's lower than the 9.6% average earnings growth estimated as of Oct. 1.
Twenty-two companies have already released earnings for the quarter, according to S&P Capital IQ. Of those, 14 have beaten analysts' estimates. Six have missed and two have met expectations.