US stock futures slid on geopolitical risks. Nasdaq 100 futures fell 0.55%; S&P futures slid 0.37%; Dow futures fell 0.29%.

The death toll from protests in Iran has reached 2,571, the U.S.-based HRANA rights group said on Wednesday, as the Islamic Republic's clerical rulers try to quash the biggest wave of dissent in years, sparking threats of U.S. intervention.

A renewed confrontation between Washington and Tehran, following an Israeli and U.S. bombing campaign against Iran last year targeting its nuclear programme, would furthers unsettle the Middle East - already battered by the two-year war in Gaza.