Australian military leaders are looking to draw on their strong ties with the new US Defence Secretary to help guide the longstanding ANZUS alliance through the uncertain Trump era.

Senior Defence figures have described General Mattis as a "sensible" and "sane" figure in the new US administration with a deep affection for Australia, who could act as a "foil" against President Donald Trump's more radical ideas.

Ties between the two countries were plunged into uncertainty yesterday with reports Mr Trump called a refugee resettlement deal the "worst ever" and accused Australia of trying to export "the next Boston bomber".

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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.

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The ABC has uncovered a recent speech delivered by the retired military commander in which he praised America's long-standing ally and the sacrifices it has made on the battlefield.

"I don't forget the debt my country owes you and we'll never forget those irredeemable debts," General Mattis told the Australian National University's Strategic and Defence Studies Centre in 2015.

In the Canberra speech titled Dealing with Threats in Tumultuous Times, the now Pentagon boss offered some advice on how he will handle growing global security threats as US Defence Secretary.

"You can't go to isolationism; you've got to work together in this world," he said.

"We're going to have to work together to address issues and I hope strongly that Australia's voice is held loud and clear."

General Mattis said when he was the head of US Central Command, overseeing the wars in Iraq and Afghanistan, he gained great admiration for Australians military leaders he worked with.

"You have a degree of moral and ethical reputation that I think could help ensure that in the future more sustainable decisions are made, including by the Americans," General Mattis told his Canberra audience.

In September last year, just two months before Mr Trump won the US presidential election, the retired US General again visited Canberra, where he addressed the United Service Institute (USI) of the ACT and met with senior military figures.

Speaking at the Australian Defence College, General Mattis spoke to the USI audience on "the gap between civil and military perspectives: Insights from Alexander the Great to Fallujah", where he again explored the threats facing the United States.

General Mattis joins National Security Advisor General Michael Flynn and Homeland Security boss General John Kelly as former military members who now sit in Mr Trump's cabinet.

Mr Trump has described General Mattis as a "true General's General", and over his military career, he has earned the nickname James "Mad Dog" Mattis.

Australian Defence leaders said a more accurate characterisation was one of a "warrior monk".

Senior Defence officials said all three generals in Mr Trump's cabinet were familiar faces to the ADF.