March 22 (Reuters) - Australian shares slumped to a three-week low on Wednesday, mirroring a sharp overnight fall on Wall Street, as investors saw U.S. President Donald Trump's struggles to push through his healthcare overhaul as a sign he may also face setbacks delivering promised corporate tax cuts.
The S&P 500 and Dow Jones Industrial Average were down more than 1 percent in their worst one-day performances since before Trump was elected in November.
The S&P/ASX 200 index fell 1.36 percent, or 78.816 points, to 5695.8 by 1239 GMT.
"[Trump's] Healthcare legislation...looks like it is slowing everything and perhaps we mightn't see any news about tax breaks this year, I think we're speculating 2018," said Ben Le Brun, a market analyst with Optionsxpress.
Financials and material stocks led the losses.
The financial index hit a three-week low, with the "Big Four" banks losing between 1.3 percent to 2.2 percent.
Materials were dragged down, following a slip in commodity prices.
Steel and iron ore futures in China fell about 4 percent on Tuesday, while copper touched a one-week low with talks to resolve a strike at the world's biggest copper mine in Chile were set to resume.
The mining benchmark slid 1.7 percent, with heavyweights BHP Billiton and Rio Tinto declining over 2 percent each.
Shares of Fortescue Metals Group plunged as much as 7.1 percent, their biggest percentage loss in eight months, while South32 Ltd lost 2.9 percent.
Healthcare stocks were another drag on the main index, falling most in three months.
CSL Ltd hit its lowest in two weeks, while Sonic Healthcare Ltd slipped 1.6 percent.
The energy index dived 1.4 percent on falling oil prices, with U.S. crude dropping to its lowest since November, as concerns about new supply overshadowed the latest talk by OPEC that it was looking to extend output cuts beyond June.
Woodside Petroleum Ltd shed 1.8 percent, extending losses to a third consecutive session, while Santos Ltd hit its lowest in a week.
New Zealand's benchmark S&P/NZX 50 index fell 0.7 percent, or 50.69 points, to 7034.85.
Losses were spread across all sectors.
Fonterra fell as much as 0.2 percent to a near five-week low.
The world's largest dairy exporter reported a 2.2 percent rise in half-year profit but cut its full-year guidance due to market volatility, reducing forecast earnings per share to 45 to 50 cents per share, from a range of 50 to 60 cents.
Reporting by Christina Martin; Additional reporting by Urvashi Goenka; Editing by Eric Meijer