U.S. stock futures pared early gains, with Dow Jones industrial average futures trading more than 15 points higher during the European morning session.
Wall Street shares closed higher on Tuesday as the Fed began its two-day meeting and investors attempted to shake off worries about the Greece debt talks.
Greece is set to default on a 1.6 billion euro ($1.8 billion) debt repayment to the International Monetary Fund on June 30 unless it receives fresh funding from its creditors, who insist Athens needs to make further reforms if it wants to unlock aid.
Later on Wednesday, the European Central Bank is expected to hold a meeting to review emergency funds, known as the Emergency Liquidity Assistance (ELA).
Greek banks are reliant on this funding and analysts warn that if the central bank curbs this liquidity, Greece may have no option but to impose capital controls.
"Unfortunately, Greece continues to dominate the daily moves, driving the current ructions in bonds, weak sentiment in stocks and fears about the credit markets. It's all about uncertainty," Bill Blain, a strategist at Mint Partners in London, said in a note. "Much more important in the long-term will be today's clues on U.S. rates from the FOMC."
European shares traded lower on Wednesday as caution ahead of the Fed and ECB meetings weighed, while in Asia, Japan's blue-chip Nikkei 225 stock index closed a touch lower—bucking a broadly positive trend in Asian markets.
The dollar meanwhile held within tight ranges against the euro and yen ahead of the Fed meeting. The euro held at about $1.1269 while the dollar was little changed around 123.84 yen.
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Companies expected to report earnings this session include FedEx Corp, Oracle and Actuant.