The Fed "could introduce new information [Wednesday], as there's a bit of uncertainty as to how they would characterize the economy. They could be more optimistic or less optimistic," said Dan Greenhaus, chief global strategist at BTIG.
"The Fed statement probably will not even hint on the timing of lifting the underlying Fed funds rate; there will possibly be one dissenting vote on that, but that's not going to cause a stir," said Fred Dickson, chief investment strategist at Davidson Companies, referring to Fed Bank of Dallas President Richard Fisher, who has called for a hike as soon as this year.
The decision from the Federal Open Market Committee will come after Wall Street gets a view on economic expansion in the second quarter, with analysts generally expecting gross domestic product grew at a 3 percent to 3.5 percent annual rate.
The government's first view of second-quarter GDP will be released at 8:30 a.m. EST with the report including revisions for the first quarter, which last had output contracting at a 2.9 percent rate.
"Assuming we get a rebound in GDP growth in the second quarter from what we saw in the first, the debate will heat up around when we'll see rate increases, between the pace and timing in early 2015," said Dunigan.
"What could happen is you could revise the first-quarter number to be less bad, and the second-quarter number to be less good; that'll drive people nuts," said Greenhaus.
On Tuesday, stocks declined, pulling the Dow Jones Industrial Average under 17,000, as the United States and European Union joined in expanding sanctions against Russia, highlighting a geopolitical crisis that overrode investor enthusiasm for earnings from companies including Merck.
Read MoreStocks fall; Ukraine concerns overtake earnings cheer
—By CNBC's Kate Gibson