Australia's fuel security could unravel within weeks, a defence expert has warned.

If a global bidding war erupts over dwindling supplies, guarantees from key Asian suppliers are set to go out the window.

The warning comes even as Energy Minister Chris Bowen set out to reassure Australians on Monday that the country's fuel supply extended beyond mid-April and 'into May'.

Bowen said normal fuel flows had been guaranteed by major exporters Japan, South Korea and Singapore, easing concerns those countries might curb exports to protect domestic supply.

But Strategic Analysis Australia director, Michael Shoebridge, cautioned that those assurances could quickly evaporate in a severe shortage, warning 'countries always meet their own needs first'.

'It's helpful to have those discussions, but the practical reality of the energy market is going to be that the supplies go to the highest bidder, and it doesn't seem to me that government assurances will change that,' he told news.com.au.

'As the energy supplies that have come out of the Gulf before the war get consumed, which will happen from about April 20, prices will go up, and government assurances won't change that. 

'We will be in a bidding war, along with many others, for more limited fossil fuel supplies.'

Prime Minister Anthony Albanese is travelling to Singapore on Thursday to meet his counterpart Lawrence Wong, as the government seeks to shore up fuel supplies by leveraging Australia’s gas exports to support oil-based fuel supply chains. 

Australia’s petrol imports are heavily reliant on Singapore, which accounts for about 55 per cent of supply, followed by South Korea at 22 per cent and India at 11 per cent, with Malaysia contributing a further 10 per cent. 

Smaller volumes are sourced from Japan, Brunei and several European nations.

Mr Shoebridge said Japan, in particular, had a highly fuel‑intensive manufacturing sector that it would prioritise in the event of a shortage.

Despite those pressures, Assistant Foreign Affairs and Trade Minister Matt Thistlethwaite said he had received pledges from Japan, South Korea and Singapore that fuel shipments to Australia would continue. 

However, at least six fuel shipments to Australia have already been cancelled or deferred, and there are expected to be further delays or cancellations.

Mr Shoebridge warned the government’s confidence overstated the degree of control countries have over commercial fuel markets.

'Mr Thistlethwaite is making it sound like the Australian Federal Government is able to dictate what our companies do, and he's assuming the same is true for Singapore and Japan - that their governments have absolute control over their refineries and who they sell their product to,' he said.

'I don't think that's true; it's still not true in Australia. We've had a very arm's length government to corporate relationship, including around energy. So there's a level of magical thinking about all this.

'Governments telling each other that they've got each other's back is interesting, but what real levers and control do they have over the real actors here, which are the companies?' 

Australia now has fuel reserves equivalent to 39 days' worth of petrol, 29 days' worth of diesel and 30 days' worth of jet fuel, with over 50 fuel shipments due to arrive in the next month. 

If the fuel supply situation does deteriorate, rationing could come quickly, experts warn.

'We're not talking about months, we're talking about a few days,' Sydney University Professor Ben Fahimnia told 9News.

'We're already seeing the early symptoms of rationing, it's just not officially declared.'

Despite US President Donald Trump announcing a two‑week ceasefire with Iran, conditional on Tehran immediately reopening the strategic Strait of Hormuz, fresh explosions rattled America’s Arab allies overnight as Iran accused Washington of breaching the agreement. 

While Trump insisted the truce was holding, Tehran declared the vital shipping lane closed in response to Israel's strikes on Lebanon.