This is what you need to know before the bell:
1. Trump's trade threat causes Asian stocks to slip. The U.S. President said he is willing to renegotiate or terminate a trade deal with South Korea
2. A passenger dragged off a United Airlines (UAL) plane has received a financial settlement. The condition of the payout is that the specific "amount remains confidential"
4. U.K. consumer confidence slides to a 4-month low as the election kicks off. Inflation, Brexit and general election worries are keeping optimism in check.