U.S. stock index futures indicated a lower open on Wednesday, after the Japanese Nikkei index fell 4 percent on renewed concerns about when the Federal Reserve will begin tapering off its asset purchases.
The Nikkei ended below the key 14,000 level and the Japanese yen hit a six-week high against the dollar, after two Fed officials — Charles Evans and Dennis Lockhart — said the central bank would likely start reducing its stimulus program this year.
U.S. stocks clocked their biggest fall since June on Tuesday after the comments, and on Wednesday, Australia's S&P ASX 200 index and South Korea's Kospi hit two-week lows.
Shares in Europe also fell on Fed concerns on Wednesday, and in the U.K., investors were focused on Bank of England Governor Mark Carney's first inflation report.
Carney unveiled Fed-style forward guidance, and said Britain's central bank will not raise interest rates until U.K. unemployment hits 7 percent.
"When Carney came in everyone expected him to be quite dovish; in fact it didn't turn out that way. He is embarking on a new path for the Bank of England," said Khoon Gon, senior FX strategist at ANZ.
Meanwhile, the Bank of Japan began a two-day policy meeting on Wednesday with an outcome due on Thursday. While analysts expect no action, the direction of the yen will hinge on the central bank's statement.
More Fed speeches are due on Wednesday, with Philadelphia Fed President Charles Plosser speaking at 12:30 p.m. ET on the economic outlook, and Cleveland Fed President Sandra Pianalto speaking at 1:40 p.m. on the regional economy in Cleveland, Ohio.
The Fed will also release consumer credit data for June at 3 p.m. Analysts polled by Reuters forecast a $15 billion gain, after a $19.6 billion rise in May.
In addition, several major second-quarter earnings reports are due before Wall Street opens on Wednesday, including Time Warner, Ralph Lauren, AOL, Holly Frontier, Wendy's, Devon Energy, Marsh and McClennan, Duke Energy and Carlyle Group. After the closing bell, there will be numbers from Groupon and Tesla Motors.
The U.S. Treasury will also auction $24 billion in benchmark 10-year notes at 1 p.m. ET, following Tuesday's strong $32 billion 3-year note auction.
"We're entering the dog days of August and that tends to benefit the Treasury market," said John Briggs, senior Treasury strategist with RBS.
—By CNBC's Katy Barnato