U.S. stock index futures pointed to a lower start to trade on Monday, as European stocks and currencies continued to decline following the U.K. vote to leave the European Union (EU).
Dow futures implied an open of more than 150 points lower, while the implied opens on the S&P and Nasdaq were 26 points and 55 points lower, respectively.
The pan-European STOXX 600 traded down 2.9 percent early on Monday. The internationally focused FTSE 100 traded 1.7 percent lower and the FTSE 250 — which tracks the next 250 biggest U.K. companies — declined by 5.2 percent.
The U.K. government is yet to indicate how negotiations to leave the EU trading bloc will proceed. Meanwhile, Prime Minister David Cameron has said he would resign by October and the leader of the opposing Labour Party faces a "vote of no confidence" on Monday.
"Day four after the seismic referendum result and the only thing that's crystal clear is that the U.K. is in the midst of one hell of a political crisis," Chris Scicluna, head of economic research at Daiwa Capital Markets, said in a note on Monday.
Major Asian indexes closed higher on Monday, with Japan's Nikkei leading gains, ending up 2.4 percent. This followed media reports that Tokyo would step in, if necessary, to stabilize the , which has gained from the safe-haven bid that followed the Brexit vote.
In the U.S. economic news, the advance May trade deficit was $60.59 billion. No major earnings were expected.
Risk aversion sent the British pound reeling to near $1.32 on Monday, within view of Friday's 30-year low.
On Friday, the Dow index tumbled 610 points and each of the major averages fell at least 3 percent.