International diplomacy experts have expressed their alarm at what they describe as a "startling" disruption to US-Australia relations this week.

Key points: Political risk consultant Ian Bremmer not confident Australia-US alliance will survive

Political risk consultant Ian Bremmer not confident Australia-US alliance will survive Former senior US diplomat Nicholas Burns says Trump's comments were "improper"

Former senior US diplomat Nicholas Burns says Trump's comments were "improper" Both agree the behaviour comes down to an inexperience in government affairs

The traditionally strong ties between the two countries were plunged into uncertainty yesterday with reports US President Donald Trump called a refugee resettlement deal the "worst ever" and accused Australia of trying to export "the next Boston bomber".

Mr Trump has since defended his comments, made in a phone call with Prime Minister Malcolm Turnbull, while US senators called Australian ambassador Joe Hockey to offer their apologies.

Mr Hockey also met with Trump adviser Steve Bannon and chief of staff Reince Priebus at the White House amid ongoing discussions over the agreement.

But one of the United States' most senior former diplomats says Mr Trump's comments were "improper" and demonstrate a callousness towards one of the country's closest allies.

Nicholas Burns spent almost three decades working for both Republican and Democratic administrations, including as under-secretary of state for political affairs.

He is now a professor of the practice of diplomacy and international relations at the Harvard Kennedy School of Government.

"There are so many challenges ahead, and the last thing you want is to have a United States Government that is suddenly arguing with its allies in public — three of them this week," Professor Burns said.

"It's rather startling and it's most unwelcome.

"What was unusual was that it leaked out of the White House, and then President Trump issued a tweet that was highly critical of the Australian Government."

Trump 'has it backwards'

Today, Mr Turnbull acknowledged Mr Trump was clearly opposed to the deal, which the President branded "dumb" on Twitter.

"We secured the commitment from the US President that we wanted and that we sought, and we thank him for making that commitment," he told Sydney radio station 2SM.

"He's been very critical of the deal but we have persuaded him of sticking to it nonetheless."

But Professor Burns said Mr Trump's comments appeared to be part of a trend.

"There's something unusual happening; the Trump administration has been aggressively critical of many of the allies — Mexico, Australia, Germany — just three this week, and yet not at all critical of Russia," he said.

"President Trump has it backwards, he ought to be tough on Russia and he ought to have a respectful, friendly alliance relationship with the Australian Prime Minister."

'These were relationships under pressure'

Ian Bremmer, a political scientist and founder of the Eurasia Group, a consultancy researching political risk, echoed Professor Burns' views.

"It's quite something that the American President would have off the bat a much warmer relationship and phone call with the Russian president than he would with the Australian Prime Minister," Dr Bremmer said.

"It's quite a dramatic change in the way we think about America's role in the world."

While he said Mr Trump's comments were alarming, he said it was not necessarily a surprise that the relationship between the US and Australia is seeing strain.

"I'm not confident that the alliance will survive in the sense that I believe that Pax Americana is over," he said.

"The geopolitical order where the United States was doing the driving and the leadership was eroding well before Trump."

According to Dr Bremmer, this is in part because of growing powers like China.

"Part of that of course is the rise of China and the creation of alternative economic architecture, which has been very important for the Australian economy," he said.

"Even if Trump were a great president on foreign policy, it was going to be hard to maintain relationships like US-Australia to the same degree they had before — these were relationships under pressure."

As for Mr Trump's latest diplomatic faux pas, both Professor Burns and Dr Bremmer attributed it to the inexperience of the Trump administration in foreign affairs.

"Many of the people have never served in government before, including President Trump — this is his first experience in government," Professor Burns said.

Dr Bremmer said: "The willingness of President Trump to do damage to existing relationships not only from his strategy but also from a complete lack of expertise in the foreign arena is very high."