Australian shares are expected to start lower after the US Federal Reserve warned of extended economic weakness from the coronavirus pandemic, rocking US markets.

The SPI 200 futures contract was down 58 points, or 1.07 per cent, to 5,366.0 at 0800 AEST on Wednesday, indicating a loss in early trade.

Fed Reserve Chairman Jerome Powell pledged to use the US central bank’s power as needed, but called for Congress to agree on additional fiscal support.

He cautioned that bankruptcies among small businesses and extended unemployment for many people remain a serious risk.

Following his comments, the Dow Jones Industrial Average ended 2.17 per cent lower at 23,247.97, the S&P 500 lost 1.75 per cent to 2,820 and the Nasdaq Composite dropped 1.55 per cent to 8,863.17.

Meanwhile in Australia, much attention will be focused on employment data for April, which will reflect the full impact of the coronavirus-related lockdowns imposed in late March.

Economists, on average expect a loss of 550,000 jobs from the virus impact, and the jobless rate to climb to 8.3 per cent.

Elsewhere, fuel refiner Caltex will hold its annual general meeting while Xero and NBN will report earnings results.

The benchmark S&P/ASX200 index closed on Wednesday up 18.9 points, or 0.35 cent, at 5,421.9 points.

The All Ordinaries closed up 16.4 points, or 0.3 per cent, at 5,513.7 points.

One Australian dollar was buying 64.56 US cents at 0800 AEST, down from 64.79 US cents at the close of trade on Wednesday.