Sept 21 (Reuters) - Australian shares fell on Wednesday, with the commodity and financial sectors leading the losses, as investors prepared for an outsized interest rate hike from the U.S. Federal Reserve to tame searing inflation.

The S&P/ASX 200 index fell about 1% by 0050 GMT, with all the subindexes in the red. The benchmark rose 1.3% on Tuesday.

Later in the global day, the U.S. central bank is largely expected to raise interest rates by 75 basis points for the third consecutive time, with some market participants pricing in a full percentage point hike.

In Australia, the mining subindex led losses, falling as much as 1.8%, after iron ore prices in China were weighed down by the country's persistent zero COVID policy, with sector majors Rio Tinto, BHP Group and Fortescue Metals shedding between 2% and 2.4%.

Additionally, the gold sector shed 2%, due to a dip in safe-haven demand following a stronger dollar, with index majors Newcrest Mining and Northern Star Resources dropping 2.7% and 2.3%, respectively.

Financials skidded 0.6%, with the country's largest banks falling in the range of 0.4% and 0.8%.

Australia's central bank said its pandemic-era bond buying program had benefits to the economy but will also cause large losses for the bank, potentially putting it into negative equity.

The domestic tech index and healthcare stocks fell 1.8% and 0.3%, respectively.

Separately, Australia's second largest grocer Coles Group agreed to sell its fuel and convenience retailing unit to power producer Viva Energy for A$300 million ($200.64 million).

In New Zealand, the benchmark S&P/NZX 50 index fell around 0.4% to 11,517.4.

(Reporting by Archishma Iyer in Bengaluru; Editing by Rashmi Aich)