Wall Street was mixed overnight ahead of the UK's referendum on the country's membership in the European Union.
US Federal Reserve Chair Janet Yellen's semi-annual testimony before lawmakers, on Tuesday and again on Wednesday, underpinned expectations the central bank won't be in a rush to raise interest rates, as she signalled concern over low productivity even as she remained upbeat about the outlook for the US economy.
Futures indicate 44 percent odds that the Fed will tighten policy this year, down from 76 percent probability at the start of the month, according to Bloomberg.
"We think that the US economy is in good shape, despite some setbacks in very recent months," International Monetary Fund Director Christine Lagarde said in prepared remarks following a review of the world's largest economy.
Even so, Lagarde warned that the US labour force participation is declining, as has productivity growth.