Disappointed by lack of promised detail on a major US stimulus plan, investors have sent Australia’s volatile share market into another deep dive.

The benchmark S&P/ASX200 index was down 95.4 points, or 1.61 per cent, at 5,844.2 at midday AEDT on Wednesday, dragged down by banks amid more pressure on rates.

Futures had pointed to a local rally on Wednesday after Wall Street soared overnight on US President Donald Trump’s promise of a major stimulus announcement to ease the impact of the coronavirus.

But after the details failed to appear as promised, sentiment soured, CMC Markets and Stockbroking chief strategist Michael McCarthy said.

Prime Minister Scott Morrison has promised to deliver an Australian stimulus package on Thursday, but investors are still focused on global macro conditions, Mr McCarthy said.

By midday the broader All Ordinaries index had fallen by 88.2 points, or 1.47 per cent, to 5907,6 points with only the energy and health care indicies marginally in the green.

Reserve Bank Deputy Governor Guy Debelle told business leaders on Wednesday the RBA was reluctant to speculate how deeply the coronavirus will hurt Australia’s growth beyond the March quarter.

But he suggested interest rate cuts and mining investment would at least help cushion the blow.

Australian Banking Association chief Anna Bligh said banks were in the “best-ever shape” to face the challenge and were well capitalised, with strong balance sheets.

But the big four banks fell amid concern about the downward pressure on rates caused by the coronavirus impact on the economy.

CBA dropped 3.18 per cent to $71.04, Westpac fell 2.08 per cent to $20.05, NAB was 3.46 per cent lower at $20.37 and ANZ declined 2.46 per cent to $20.37.

Oil prices rallied overnight on stimulus hopes, and as parts of Hubei province, which was the epicentre of the coronavirus outbreak, start to return to normal.

Local oil stocks rose at the start of trade but by midday Woodside Petroleum was 10 cents lower at $21.90 while Santos remained higher, up 1.93 per cent at $5.01.

Health stocks were marginally higher as market heavyweight CSL climbed 2.79 per cent to $311.76.

Newcrest lost 7.69 per cent to $26.90 after downgrading its production forecast and Webjet fell 1.51 per cent to $7.19 after withdrawing its guidance amid rising last minute cancellations.

The Australian dollar was buying 64.92 US cents at noon AEDT, down from 65.62 US cents at the market close on Tuesday.