Australia's share market has broken multiple records as investor confidence surges on hopes for an imminent US-Iran peace deal.

The S&P/ASX200 closed at a record-high 9,225.7 on Wednesday, up 82 points, or 0.9 per

cent, as the broader All Ordinaries rose 93.5 points, or one per cent, to 9,405.4.

The top-200 also hit a fresh intraday peak of 9,230, beating February's high-water mark that was set days before US-led attacks on Iran sparked major conflict and the biggest disruption to oil supply volumes in recent history.

Brent crude prices fell to three-week lows of $US78.11 a barrel on reports the US and Iran were close to a deal to end fighting and fully reopen the Strait of Hormuz shipping route.

The Australian dollar is buying 70.49 US cents, up from 70.14 US cents on Tuesday at 5pm AEST, as metals prices improved and investors sold down the safe-haven greenback.