US stock futures tread water after S&P 500 hits record high, as focus narrows in on Jerome Powell's Jackson Hole speech

• US stock futures were roughly flat on Wednesday after the S&P 500 hit a record high on Tuesday.
• Investors are focused on the Fed's Jackson Hole meeting, where its chair Jerome Powell will talk Friday.
• Powell's speech will be scrutinized for signals about the future path of the Fed's monetary policy.

US stock futures fluctuated around the flatline Wednesday after the S&P 500 index hit another record high the day before, as investors awaited a key speech by Federal Reserve Chair Jerome Powell.

S&P 500 futures were little changed, while Nasdaq 100 futures climbed 0.1%. Dow Jones futures were also roughly flat.

In Europe, the continent-wide Stoxx 600 rose 0.14%. Asian stocks mostly moved higher overnight, with China's CSI 300 up 0.2%.

It's been a relatively quiet few weeks for stock markets, with the S&P 500 consistently hitting new highs despite a dip last week after US retail sales underwhelmed investors.

Strong stimulus from central banks and governments, the reopening of economies and the rollout of coronavirus vaccines are all supporting equities. However, rising Delta variant coronavirus cases, hot inflation and signs of labor and supply shortages are worrying some market participants.

The key event for traders and investors this week is Federal Reserve Chair Jerome Powell's speech on Friday at the Jackson Hole Symposium - a virtual meeting of the world's top central bankers that starts Thursday.

Powell's words will be scrutinized for any sign about when the central bank will start reducing its support for the US economy, which has grown rapidly in 2021, by winding down its bond purchases.

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"The economy is now reaching the bar set by the Fed," said Hugh Gimber, global market strategist at JPMorgan Asset Management. "Jackson Hole is unlikely to be the setting for a formal taper announcement, but Powell's remarks should still strike an upbeat tone."

"With the recovery making strong progress, and the labour market gathering steam, the US economy no longer needs the same amount of support," Gimber said. "Equity markets continue to cheer the amount of liquidity in the system, but the Fed will not be blind to the longer-term risks of policy that is too supportive for too long."

US bond yields, which move inversely to prices, fell slightly on Wednesday, with the key 10-year US Treasury yield marginally lower at 1.288%. The dollar index was up 0.08% to 92.97, however.

Oil prices have climbed sharply in recent days as coronavirus cases have fallen in China, but slipped back slightly on Wednesday. Brent crude oil was down 0.27% to $70.22 a barrel, while WTI crude was 0.27% lower at $67.36 a barrel.

In the cryptosphere, bitcoin slipped back after topping $50,000 for the first time since May. It was down 2.14% to $47,313 on Wednesday.

"The breakout failed to generate renewed momentum, which may suggest the rally is running on fumes," said Craig Erlam, senior market analyst at trading platform Oanda. "That's no bad thing in the longer run, with there being a lot of optimism out there about cryptos."