In exchange for American attacks being put on hold for two weeks, Iran had agreed to allow tankers to resume travelling through the critical shipping route, which carried around one-fifth of the world's oil before the war.
But deadly attacks by Israel on Lebanon overnight has raised questions about the truce, with Iran saying the agreement included Lebanon, at odds with the US and Israel.
Foreign Minister Penny Wong said she hoped the ceasefire would hold.
"We all know the cease fire is fragile and that there is a long way to go in these negotiations, but we know it is necessary," she told ABC News on Thursday.
"We've seen the impact on global markets, we see it on the news, but most importantly, we see it every time we go to the petrol station to fuel up."
Senator Wong has urged Australians to temper their expectations.
"Even if the ceasefire does continue to hold - and we all hope it will - we know that global markets and the fuel and particularly energy supply, will continue to be disrupted for some time," she said.
Following initial news the strait had reopened, American oil benchmark Brent Crude plunged 13 per cent to about $US95 a barrel.
But experts and industry insiders told AAP Australian petrol and diesel prices were unlikely to respond straight away.
Australian Institute of Petroleum chief executive Malcolm Roberts, who represents major petrol companies including Ampol, BP, Mobil and Viva Energy, said a ceasefire would take some time to flow through supply chains.
"We would caution people from expecting this will have immediate effects on supply or prices in our region," he said.
If a ceasefire held, petrol and diesel prices would likely begin dropping over coming months as fuel companies sold out of their more expensive fuel, Australian National University supply chain lecturer David Leaney said.
"While that expensive oil is making its way around the world and being refined into fuel with a higher cost, that cost (of petrol and diesel) stays high for a couple of months," he said.
NRMA spokesman Peter Khoury said the organisation would watch closely to ensure falling wholesale prices were passed on in full.
"Australians have been paying the highest price on record for more than a month. We need to get relief back into family budgets," he said on Wednesday.
Prime Minister Anthony Albanese had a phone call with His Majesty the Sultan of Brunei on Wednesday, where the importance of ensuring global energy supply chains were kept open was discussed.
As Mr Albanese prepares to travel to Singapore on Thursday for talks aimed at further shoring up Australia's fuel supplies, the opposition has called for a public database of how much petrol and diesel are in the nation's reserves.
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