As of 4:15 a.m. ET, Dow Jones Industrial Average futures were 59 points lower, or 0.35% to 16980. S&P 500 futures fell 8 points, or 0.40% to 2003, while Nasdaq 100 futures were down 22 points, or 0.49% to 4353.
European shares opened slightly lower on Tuesday, following losses in Asia overnight, although SABMiller soared after accepting a 68 billion-pounds $104.48 billion takeover proposal from rival Anheuser-Busch .
The pan-European FTSEurofirst 300 index was down 0.8 percent while the euro zone's blue-chip Euro STOXX 50 dropped 1 percent.
Miners and auto sector stocks were the top sectoral fallers in early trading and investors were also awaiting the ZEW investor sentiment readings for October later on Tuesday.
SABMiller rose 9 percent and Anheuser-Busch was up 3.8 percent. SABMiller said it had indicated to AB InBev that its board would be prepared to accept the offer and said it had asked for a two-week extension to Oct. 28 of a deadline set for its rival to announce a firm intention to bid.
SAP was 4.8 percent higher after Europe's biggest software maker on Tuesday reported a 19 percent rise in third-quarter operating profit, beating the most optimistic analyst estimate.
But LVMH fell 3 percent after the luxury goods industry leader posted a mixed set of third-quarter revenue figures that revealed a strong rebound in cognac sales, particularly in China, but a slowdown at its key fashion and leather business.
(Reporting by Danilo Masoni; Editing by Sudip Kar-Gupta)