Leaders of the U.S. Senate Foreign Relations Committee said they had drafted authorization for the limited use of military force in Syria, and have set a time limit of 60 days for any action, with a 30-day possible extension. The measure will now be voted on by the full Senate on September 9.
(Read more: Why oil prices may remain strong, war or no war)
Investors also await the G-20 summit of the world's 20 largest economies on Thursday, where Syria is likely to be in focus again. The summit takes place in Russia, which has locked horns with the U.S. over Syria, due to its strongly non-interventionist stance.
On the economic front, the U.S. trade deficit increased 13.3 percent to $39.1 billion in July, according to the Commerce Department. Economists polled by Reuters had expected the trade deficit to rise to $38.7 billion.
The Federal Reserve will publish the latest edition of the Beige Book, its region-by-region assessment of the economy at 2pm ET.
Weekly mortgage applications climbed for the first time in four weeks as rates declined from their highest level this year, although demand for purchase loans dipped, according to the Mortgage Bankers Association.
The Labor Department is expected to release its widely-watched employment report on Friday, ahead of the Fed's September policy-setting meeting. Economists polled by Reuters expect non-farm payrolls to have increased by 180,000 obs last month, up from a gain of 162,000 the month prior.
"The non-farm payrolls report for August released on Friday will likely prove far more crucial (than Wednesday's data), given the importance of labor market conditions and as such will likely generate a much greater reaction in financial markets," said Bank of Tokyo-Mitsubishi's Lee Hardman in a research note.
Among earnings, Dollar General climbed after the value retailer posted quarterly results that topped Wall Street expectations, thanks to strong demand for its perishables, snacks and recently-added tobacco products.
H&R Block slumped after the tax preparer posted a wider-than-expected quarterly loss.
In other news, the Bank of Japan kicked off a two-day monetary policy meeting on Wednesday. While no new policy action is expected, the Asahi newspaper reported that the central bank may consider further easing if Prime Minister Shinzo Abe decides to hike sales taxes.