In the first half-hour of trading, the Dow Jones industrial average fell 26 points to 13,358. The Standard & Poor's 500 index lost two to 1,459. The Nasdaq composite index rose a point to 3,100.
Aluminum maker Alcoa reports its fourth-quarter financial results after the market closes, marking the unofficial kickoff to weeks of earnings announcements from U.S. companies. Analysts surveyed by FactSet expect Alcoa to earn 6 cents per share, after losing 18 cents per share in the same quarter a year earlier.
Market-watchers expect the quarter's results could include many surprises because of events like Superstorm Sandy, the presidential election, and the narrowly avoided tax increases and spending cuts known collectively as the fiscal cliff.
Trading has been cautious in the week since Congress and the White House struck a deal to maintain lower tax rates and postpone painful cuts in government spending. Enthusiasm about the compromise pushed the Dow up 300 points last Wednesday, its biggest gain since December 2011.
In corporate news:
— Agriculture products giant Monsanto's shares jumped 3 percent after saying its profit nearly tripled in the first fiscal quarter, helped by strong seed sales in Latin America. Monsanto raised its earnings guidance for the year. Shares rose $3.04 to $98.98.
— Video game seller GameStop Corp. lost 7 percent after reporting weak holiday-season sales and cutting its revenue guidance. Shares dropped $1.71 to $23.04.
— Yum! Brands Inc., operator of the KFC and Taco Bell fast food chains, dropped 5 percent after saying a key sales metric in China fell more than expected in the fourth quarter. The decline was related to problems at two of its small chicken suppliers; nearly half of the company's revenue came from China in 2011. Shares fell $3.42 to $64.47.
— In Korea, electronics giant Samsung said it expects record earnings for the fourth quarter as shoppers continue to embrace its smartphones and tablets. But there were signs its momentum is slowing, and shares of the company closed down 1.3 percent in Seoul.