The S&P 500 closed modestly lower after a volatile week in which investors braced for escalation between Israel and Iran, and amid signs of a split at the Federal Reserve over when to renew cutting interest rates.

Part of the lacklustre trading on Friday (Saturday AET) reflected the pending expiration of $US6.5 trillion of options known as “triple witching”. A closely watched gauge of chip shares slid after the Wall Street Journal reported the US may revoke waivers for allies with semiconductor plants in China, which could reignite trade tensions.