Australian shares were flat at Wednesday's close but registered a fresh 52-week high for the third straight day as investors braced for expected rate cuts after the US Federal Reserve's monetary policy meeting.

The S&P/ASX 200 was little changed to close at 8,142.10.

The index continues to hover at its one-year peak, above the previous record of 8,114.70 points last Aug. 1.

Investors continue to debate on how large the upcoming rate cut from the Federal Open Market Committee meeting will be, with 65% now expecting the cut to be 0.5%, Reuters reported.

Meanwhile, the report said that Kristina Clifton, an analyst for Commonwealth Bank of Australia (ASX:CBA), expects the rate cut to be at 0.25%, "because history shows that the FOMC needs a good reason to start their cutting cycle with more than a 25 [basis points] cut."

"A 50 bps cut that scares markets about U.S. economic prospects could increase the USD because it is a safe haven currency," Clifton added.

In corporate news, Harvey Norman (ASX:HVN) is facing class action proceedings for allegedly providing "little to no value" for its Product Care service. The retailer said that it will "vigorously" defend its position against the suit, adding that it has "complied with relevant laws at all times."

Shares of mining firm Future Battery Minerals (ASX:FBM) plummeted 18% at market close after it agreed to lower the deferred consideration payable by Rocktivity Nepean for the sale of certain Nepean nickel project tenements to about AU$1.04 million from AU$7.2 million.

Imugene (ASX:IMU) secured an orphan drug designation from the US Food and Drug Administration for Vaxinia, a treatment candidate for bile tract cancer. Its shares ended 6% higher.