Wall Street to mull World Bank downgrade

U.S. stock index futures pointed to a lower open on Wednesday, as shares in Europe traded lower after the World Bank downgraded its global growth outlook.

The organization cut its 2014 outlook to 2.8 percent from 3.2 percent, citing damping expansion in the U.S. in the first half of the year, unrest in Ukraine and China's economic rebalancing.

Read MoreWorld Bank: 'Prepare for next crisis now'

The day will be quiet one for U.S. economic data, with just the monthly Federal budget statement and weekly mortgage applications.

No major companies are due to report quarterly earnings.

U.S. stocks were little changed on Tuesday. However, the Dow still managed to eke out its fourth consecutive record high and benchmark 10-year Treasury bond yields hit a one-month peak.

According to news reports, Islamist militants took control of the northern city of Mosul in Iraq on Tuesday, after four days of heavy fighting. Prime Minister Nuri al-Maliki has asked parliament to declare a state of emergency that would give him extraordinary powers to tackle the crisis, according to Reuters.

Oil prices were marginally higher on the news, with commodity investors gearing up for the latest OPEC meeting in Vienna on Wednesday.

Read MoreOil spike eyed as Iraq violence escalates