Malcolm Turnbull sounded unfazed on Tuesday after explosive reports Donald Trump bragged about highly classified secrets of an ally during a meeting with Russia's Foreign Minister Sergey Lavrov.

The US alliance remains the "bedrock" of Australia's security, Turnbull declared - just as have a dozen serving prime ministers before him.

As to questions about intelligence matters, Turnbull would only say he'd adopt "my normal circumspection and discretion".

But Trump's presidency is anything but normal.

Ever since the US intelligence agencies raised concern in January about Russian interference in the US election, and the FBI began probing possible links between Moscow and the Trump campaign, you can bet American friends and allies began wondering if their secrets would be safe.

This wasn't initially considered much of a risk - at least in Australia, I was told - nor was there grave concern about Trump's pledge to allow torture during interrogation of suspects.

But four months of Trump chaos later, the question must be asked again. Russia would certainly love to see the official trust in America's spy agencies further crumble and given Lavrov was in the room with Trump when the supposed secrets were blurted out, it seems little wonder the story leaked.

Australia is one of the allies who have historically passed on top secret intelligence to the US, in return gaining access to a treasure trove of US classified material.

It was a relationship founded during the Cold War, and includes Britain, Canada and New Zealand - the so-called "Five Eyes". The deal offers enormous potential benefit to Australia, with access to a far broader view of the world than it could afford to gather alone.

The US also benefits, exposing key Australian officials to American perspectives.

But paradoxically, in a business that deals in secrets and deception, trust is the most valuable commodity.

And trust is exactly what Trump's antics call into doubt.

The White House attacked the Washington Post story "as reported" but late on Tuesday Trump defended his decision to share information, saying he wanted Moscow to do more against Islamic State.

It certainly sound credible that Trump would boast, "I get great intel. I have people brief me on great intel every day."

Oh, really, Mr President? Do tell.