Shanghai and Hong Kong retreated while Tokyo and South Korea advanced.
Wall Street's benchmark S&P 500 declined 0.1% from the previous day's record but ended August with a 2.9% gain.
Investor optimism about stronger U.S. corporate profits and that the Federal Reserve will keep interest rates low is being tested by data showing the delta variant is weighing on economic activity.
Powell's comments are “slowly being overshadowed by mixed economic data" as the virus impact “becomes more obvious,” said Venkateswaran Lavanya of Mizuho Bank in a report.
On Tuesday, a U.S. business group, the Conference Board, reported consumer confidence fell sharply in August. Most of the decline was tied to the delta variant, which has inundated hospitals with patients.
The Shanghai Composite Index gained less than 0.1% to 3,544.95 and the Nikkei 225 in Tokyo rose 1.2% to 28,425.54. The Hang Seng in Hong Kong advanced 0.2% to 25,920.16.
The Kospi in Seoul added less than 0.1% to 3,200.29 while Sydney's S&P- ASX 200 shed 0.5% to 7,499.10. New Zealand, Singapore and Bangkok gained while Indonesia declined.
Also Wednesday, a survey found Chinese manufacturing decelerated in August as demand weakened and factories struggled with supply disruptions. The monthly purchasing managers' index by business magazine Caixin fell to 49.2 from July 50.1 on a 100-point scale on which numbers above 50 show activity growing.
Investors are trying to figure out which industries gain and which will lose as they grapple with supply disruptions, the spread of the more contagious variant of the virus and signs of possible consumer caution.
On Wall Street, the S&P 500 lost 6.11 points to 4,522.68. The Dow Jones Industrial Average fell 0.1% to 35,360.73 and the Nasdaq slipped less than 0.1%, to 15,259.24.
On Friday, the Labor Department is due to report U.S. employment conditions in August.
In energy markets, benchmark U.S. crude rose 33 cents to $68.83 per barrel in electronic trading on the New York Mercantile Exchange. The contract fell 71 cents on Tuesday to $68.50. Brent crude, used to price international oils, gained 28 cents to $71.91 per barrel in London. It fell 42 cents the previous session to $72.99.
The dollar rose to 110.21 yen from 110.00 yen. The euro declined to $1.1805 from $1.1812.