Crude oil prices rose 1.5% in early Asian trading following the Iranian attack, after rising more than 2% on Tuesday, according to Bloomberg. Meanwhile, Tokyo and Sydney stocks fell, with the S&P 500 sliding 0.9%, and the U.S. benchmark index was expected to fall further in early trading.

The U.S. technology sector was the worst performer on Tuesday as the conflict in the Middle East overshadowed signals from U.S. economic data. The U.S. ISM price index posted its biggest drop since May 2023.

Evercore ISI said the new data could weigh on 10-year Treasury yields, the dollar and employment services stocks, even if Friday's jobs report is more influential.

US vice presidential candidates J.D. Vance and Tim Walz will woo key swing voters in the only debate.

In money markets, swap traders are betting there is a one-in-three chance that the Fed will cut rates by another half a percentage point in November, but BlackRock CEO Fink believes the forward curve shows too much easing.