Stock futures add to gains after CPI

U.S. stock -index futures signaled a higher open on Wednesday as investors waited to see whether the recent slide in oil prices and ongoing market volatility will lead to a dovish statement from the Federal Reserve.

Futures added to gains after data had the Consumer Price Index down 0.3 percent in November, the largest monthly drop since 2008.

The Federal Open Market Committee is gathering for a second day to discuss the timing and size of any future interest rate hikes, with a statement scheduled for release at 2 p.m. Eastern. The Fed's statement will be closely watched, with some investors expecting it to no longer say it will keep rates near zero "for a considerable time."

Read MoreThe Fed could soothe markets Wednesday

A trader works on the floor of the New York Stock Exchange during a press conference with Janet Yellen.
Jin Lee | Bloomberg | Getty Images
A trader works on the floor of the New York Stock Exchange during a press conference with Janet Yellen.

Fed Chair Janet Yellen will brief the media at 2:30 p.m.

Brent futures fell more than 1 percent on Wednesday, down for a sixth straight session, with persistent worries of a supply glut keeping prices near a 5-1/2 year low, under $60 a barrel. U.S. crude dropped 64 cents to $55.29 a barrel after touching the lowest since May 2009 at $53.60 on Tuesday.

Read MoreRussia's ruble rout: Why it shouldn't surprise you

Russia's economic turmoil remains at the forefront of investors' minds, as global markets watch to see what the government will do to halt the ruble's slide. The country's central bank has already hiked rates to 17 percent, and its finance ministry announced on Wednesday that it had started selling its foreign currency stock.

U.S. stocks fell for a sixth session in seven on Tuesday, after another day of gyrations, as equities tracked the price of oil and pondered the impact of lower energy costs and Russia's economic trouble.

Read MoreOil stocks push Europe shares lower; Fed eyed

European shares were lower in morning trade on Wednesday, with energy and mining stocks once again weighing on the wider benchmarks.

Major earnings on Wednesday include FedEx, General Mills and Joy Global before market open. Numbers from Oracle, Apogee, Jabil Circuit, Worthington Industries are expected after the bell.