Before the opening bell, Dow futures traded more than 100 points lower, following declines in European stocks and most Asian equities. The Shanghai Composite managed to post a mild gain nearly 0.2 percent despite the weak report.
"I think (the China data) is helping exacerbate the issue," said Mark Luschini, chief investment strategist at Janney Montgomery Scott.
"We had a couple of earnings after the close yesterday that the market couldn't react to, maybe setting the tone for earnings season that so far hasn't been met with strong results," he said.
China's dollar-denominated imports plunged by a worse-than-expected 20.4 percent in September from a year earlier, while exports slipped 3.7 percent, producing a trade surplus of $60.34 billion, official data showed on Tuesday.
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"I think this is not anything new for anyone," said Tom Siomades, head of Hartford Funds Investment Consulting Group. "This has been going on for months now. I think the impact is lessening to some point now. You're not getting these crazy, volatile days."
The focus for investors is third-quarter earnings season, which gets underway Tuesday with Johnson & Johnson before the bell and Intel and JP Morgan Chase after the close.
Johnson & Johnson reported earnings that beat but missed on revenue. Separately, the firm announced a $10 billion share repurchase. The stock closed down 0.56 percent.
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S&P 500-listed corporations are expected to post a 5.3 percent decline in third quarter 2015 earnings growth, the first third-quarter decline in six years, according to consensus data from S&P Capital IQ. However, excluding the energy sector drag of a sharp negative 65.6 percent, S&P 500 earnings growth would be 2.7 percent.
Nick Raich, CEO of The Earnings Scout, noted that the first 26 S&P 500 quarterly reports showed an average growth of 10.9 percent from last year, while revenue has declined about 0.82 percent.
"Earnings aren't the problem. It's the sales," he said, noting some additional pressure on stocks Tuesday from the weaker-than-expected Chinese trade data. "China data are really telling the story too that demand for foreign goods in China (is) down."
The U.S. dollar held mildly lower against major world currencies, with the euro above $1.138 and the yen at 119.74 yen against the greenback.
"We're trapped in a range," John Caruso, senior market strategist at RJO Futures, said of the steady levels in currencies. "We're waiting for the next central bank (meeting)."
"Central bank policy trumps everything," he said, "but we might be faced with the realization that earnings expectations are not as strong as they have been."
The European Central Bank meets next week, and the Federal Reserve holds its meeting in two weeks.
Federal Reserve Governor Daniel Tarullo said in a CNBC interview Tuesday afternoon that it is not appropriate to raise rates based on the current environment.
Earlier, St. Louis Fed President James Bullard said in a Reuters report that conditions support a rate hike. However, he said that as a practical matter, the economic data out since the September meeting is unlikely to convince other policymakers to increase rates when the Fed meets at the end of the month.
Bullard will become a voting member of the Federal Open Market Committee in January.
The remarks come after mixed comments from various Fed members over the past couple of days, with centrist Dennis Lockhart reiterating the case for an interest rate lift-off this year and Lael Brainard calling for no change given downside risks.
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"The Fed — certainly they didn't raise rates but it was a temporary pause. We are closer to a tightening cycle than a loosening cycle," said Doug Cote, chief market strategist at Voya Investment Management.
The Democrat Presidential debate comes in the evening.
In economic news, U.S. small business confidence rose 0.2 in September to 96.1 as stock market volatility raised concerns about sales growth, the National Federation of Independent Business said Tuesday. The organization said the level was consistent with a 2.5 percent annualized growth rate.