US stocks slipped in early afternoon trading on Wednesday, weighed down by a fall in oil prices, while caution reigned ahead of Thursday's major political and economic events. Oil prices fell more than 4 percent due to an unexpected rise in US crude inventories and took a toll on the energy sector, which dropped 2.1 percent.
Exxon's 0.7 percent fall and Chevron's 1.3 percent fall were among the biggest drags on the S&P 500 and the Dow.
Investors are also keeping a watch on Britain's general election, the European Central Bank's policy meeting and former FBI Director James Comey's testimony before a Senate panel on Thursday. Opinion polls have shown British Prime Minister Theresa May's lead over the opposition Labor party narrow over the last three weeks, with some even suggesting she could fall short of a majority government. The election could determine whether the country has a smooth or hard exit from the European Union.
"If the Conservative party extends its majority, markets will be pretty calm, but anything less than that is going to have people worried about how we approach the Brexit negotiation," said Luke Hickmore, senior investment manager at Aberdeen Asset Management.
The ECB will also hold its policy meeting on Thursday and is expected to reiterate its plan to extend the money-printing scheme at least until the end of the year.
At 12:53 pm (1653 GMT), the Dow Jones Industrial Average was down 13.5 points, or 0.06 percent, at 21,122.73 and the S&P 500 was down 3.46 points, or 0.14 percent, at 2,425.87.
The Nasdaq Composite was down 5.79 points, or 0.09 percent, at 6,269.27. Seven of the 11 major S&P 500 sectors were higher, with the financial index's 0.78 percent rise leading the advancers.