U.S. stock index futures held mildly lower after a solid two-day rally that many attributed to expectations the Fed would not raise rates.
In Europe, the pan-European Stoxx 600 index was slightly lower, with investors keenly awaiting the Fed's decision. In Asia, the Shanghai Composite index closed down 2.08 percent amid volatility, while Japan's Nikkei finished 1.43 percent higher.
In economic news, initial jobless claims declined slightly to 264,000. August housing starts fell about 3 percent.
The Philly Fed Index is released at 10:00 a.m.
On the earnings front, Rite Aid reported before the bell. Adobe Systems was expected to report after the bell.
Rite Aid posted quarterly profit of 2 cents per share, compared to estimates of 4 cents a share, though revenue was above forecasts. The drug store chain also trimmed its earnings guidance slightly to reflect recent sales trends and additional amortization expense from its acquisition of pharmacy benefits manager EnvisionRX.
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In oil markets, Brent crude traded near $49 a barrel, down about 1.5 percent, while U.S. crude was at $46.70 a barrel, down about 0.9 percent.
--CNBC's Patti Domm contributed to this report.