A former Australian ambassador to the United States has urged Australians not to worry about US President Donald Trump's latest criticism.

Trump overnight called out Australia and other allies for failing to take up arms in the war with Iran, which the US launched on February 28 alongside Israel.

'Japan didn't help us. Australia didn't help us. South Korea didn't help us. And then you get to NATO. NATO didn't help us,' Trump told a press conference.

It marked the third time Trump had directly condemned Australia for staying out of the conflict. 

Ex-Liberal senator Arthur Sinodinos described Trump as fickle, meaning strong sledges against Australia don't hold much weight. 

'I think the important thing to understand about President Trump - and his behaviour in the Iran war confirms this - is that to accept that he reserves the right to change his mind, to change his point of view, to change his rhetoric to suit the advantage of the situation as he sees it in that particular moment,' he told NewsWire.

Trump's war in the Middle East has been widely criticised across the globe for causing major economic turmoil, particularly in regards to surging fuel prices triggered by Iran's closure of the Strait of Hormuz.

On top of that, it's understood Trump expected the war in Iran to be over in a matter of weeks, not months.

Mr Sinodinos suggested the president could be lashing out at his allies due to 'frustration that things are not going his way'.

'He's really lashing out at allies because things are not going his way on the battlefield as he expected when he launched this war a few weeks ago,' he said.

Trump's first sledge against Australia came in March when his calls for allied navies to force open the Strait of Hormuz were ignored by the international community.

He followed the radio silence with an emotional post to social media. 

'Because of the fact that we have had such Military Success, we no longer 'need', or desire, the NATO Countries' assistance - WE NEVER DID!' he wrote.

'Likewise, Japan, Australia, or South Korea. 

'In fact, speaking as President of the United States of America, by far the Most Powerful Country Anywhere in the World, WE DO NOT NEED THE HELP OF ANYONE!'

Since then, Trump has repeatedly threatened to worsen the attacks on Iran - including last week when he vowed to bomb Iran 'back to the stone ages'.

Australian Prime Minister Anthony Albanese on Tuesday reiterated calls for 'de-escalation' and for Trump to share 'clear objectives' for the war.

'The objectives that President Trump outlined at the beginning of the process have largely been achieved,' Albanese told a press conference.

'This is a conflict that is having a massive impact on the global economy, in particular having a massive impact here in Australia, as it is, right around our region and right around the world.'

Mr Sinodinos said Trump was likely hoping America's allies would step in to assist in the conflict but added Australia had little incentive to do so, given its interests are primarily in the Indo-Pacific region.

However, he warned the Albanese Government to remember Trump 'is a transactional leader'.

'Just as we want the United States to be more present and engaged in the region, we have to keep finding ways to present this in a way that's of benefit to them as well,' Mr Sinodinos said.