Major averages have been volatile since Bernanke said last month that the Fed could begin to pare back its stimulus efforts if the U.S. economy gains momentum. Stocks rallied on Monday and Tuesday this week on the idea that Bernanke will not signal an abrupt end to the bond purchasing program.
The Fed is also expected to provide an update on its economic projections for 2013-2015. The Fed's latest projections, made in March this year, saw real GDP growth at around 2.6 percent in 2013 and 3.2 percent in 2014. In terms of unemployment, the Fed projected a rate of around 7.4 percent in 2013, improving to around 6.9 percent in 2014.
President Barack Obama added to uncertainty about Fed policy on Tuesday, when he gave a press interview in which he suggested that Bernanke would leave at the end of his term in January. Obama said Bernanke had "already stayed a lot longer than he wanted or he was supposed to".
(Read More: Obama 'Essentially Fired' Bernanke: Meyer)
Fed Vice Chairman Janet Yellen is widely seen as the leading candidate to replace him, but there are other possibilities, including former Treasury Secretary Larry Summers. Yellen's views are viewed as similar to those of Bernanke.
(Read More: Why Yellen Should Be Next Fed Chief: Ex-Official)
In Europe, Obama will address crowds at Berlin's famous Brandenburg Gate on Wednesday. He is likely to call for closer trade relationships and renewed activism on climate change in a speech.
Later in the day, Japanese Prime Minister Shinzo Abe will speak in London at 1 p.m. about his economic program, which could add to market jitters prior to the Fed announcement.
In company news, FedEx reported a bigger-than-expected quarterly profit, thanks to its ground shipment business and amid lower jet fuel prices. But the company, considered a bellwether for economic activity, issued disappointing guidance.
Adobe surged after the software maker beat earnings expectations and said it expects the number of paid subscribers for Creative Cloud in the current quarter to top the 221,000 subscribers who signed up in the second quarter, increasing the total to 700,000.
Micron Technology, Red Hat and Jabil Circuit are expected to post earnings after the closing bell.
Dell traded flat after billionaire investor Carl Icahn promised the tech company's shareholders that the company would buy back up to $16 billion of stock if they join his move to stop Michael Dell and Silver Lake Partners's proposal to take the firm private.
Meanwhile, Dish Network Corp said it would not make a new offer to buy No. 3 Sprint Nextel, and would instead focus on its tender offer for Clearwire Corp.The decision may be good news for Japan's SoftBank, which is also trying to buy Sprint.
On the economic front, interest rates on home mortgages gained for the sixth-straight week to hit their highest level in over a year, according to the Mortgage Bankers Association, pushed higher by worries that the Fed could slow its stimulus program sooner than expected.