- As investors processed the Federal Reserve's most recent hawkish comments and growing evidence of a global economic downturn, US index futures struggled to find direction.

- Ahead of this week's Jackson Hole central bankers retreat, futures on the S&P 500 and Nasdaq 100 wavered between little gains and losses. The rate on 10-year government bonds remained above 3%, and the dollar stayed stable.

- Investors will closely examine Fed Chair Jerome Powell's Friday address at Jackson Hole to get a sense of how aggressive the US central bank will be in the face of escalating economic difficulties. Equities have failed to recover globally from their June low in advance of the hotly anticipated event.