Scott Morrison is Donald Trump's kinda guy.

You can imagine it in Trump's internal monologue — what's not to like about the Australian PM?

He's a winner: a conservative political success who was underestimated by his knockers. Just like me!

This Morrison guy leads a country that buys more stuff from the United States than the US buys from the Aussies. Now that's the sort of trade Trump loves.

Making it ever sweeter for the US President is that Australia pulls its weight militarily, not like those European NATO freeloaders who lean on America's might. At my expense!

By comparison, those folk Down Under have promised to get their defence spending to 2 per cent of GDP by 2021. That's so great, SO GREAT!

The Prime Minister's task is to gently steer Donald Trump in the direction of Australian interests. ( AP: Manuel Balce Ceneta )

Even better, those Aussies don't come asking for anything.

Yeah sure, there was that guy before (Malcolm Trumble, was it?) who insisted the US take 1,250 refugees off Australia's hands — that was my most unpleasant call — but at least Trump could blame that "rotten" deal on Barack Obama when he reluctantly agreed to abide by its terms.

Scott's different to Malcolm. He's my mate. I LOVE that word. Mate!

The Prime Minister's challenge is to use this personal vantage point to gently steer the United States towards Australia's benefit, without it being seen as demanding.

Scott Morrison and wife Jenny have arrived in Washington DC ahead of a state dinner. ( AAP: Mick Tsikas )

Trump's interests don't gel with Australia's

The truth is that Morrison sees the world quite differently to Trump. The trick for him is to not let on.

The Trump-Morrison relationship must — by reasons of personality and strategy — be a case of public support alongside careful, private advocacy.

Scott Morrison's interests on Iran and China don't align with the US. ( ABC News: Andrew Kennedy )

For as much as Trump sees some of himself in Morrison, very few of Trump's top-line agenda items are in Australia's interests, whether it is the US trade war with China or America's slow drift towards military conflict with Iran.

As one shrewd ex-diplomat puts it: "Trump's a bundle of instincts rather than someone with a clear world view or a sharp geopolitical strategy."

Morrison's got excellent political instincts and a keen sense for what is good for Australia and, much more importantly in this context, what is not.

Trump is essentially transactional, but his desire for adoration and affirmation is a clear weakness.

Morrison is open to deals but is acutely aware of the dangers of sycophancy, as shown in his cautious and conditional Australian contribution to a US-led operation to secure the shipping lanes in the Strait of Hormuz.

Australia would resist being dragged into American military confrontation against Iran, and would counsel against it.

Of worry too is that Trump and some of his senior lieutenants show little regard for the liberal world order comprising global institutions, international laws and norms or global concepts of the public good, of which the US has long been the guardian.

Trump and co reckon this framework has screwed America over decades, to the advantage of the likes of China.

What troubles Australia is that Trump is under pressure from his administration's hawks to decouple the US from this established way of doing things — and potentially split global supply chains to ostracise China.

This would not be in Australia's economic interests. Not one bit. Think iron ore, coal and foreign students.

The plan after Trump

But while the US has strayed from international engagement, especially in regard to China, Trump's America hasn't decided what the replacement approach should be.

Thank goodness too, because this gives Morrison time. Australia, as a middle power, can't buy or bully its way in the world.

Morrison needs Trump to mend relations with China, not deepen conflict. ( ABC News )

The rules once considered orthodox in the post-war era — the rules that have had the US at its apex before Donald Trump's disruption — have been to Australia's gain.

Australia's security and prosperity are best served if the US remains deeply involved in that arrangement.

As Australia sees it, the US has responsibilities that will persist long after Trump's economic and strategic myopia passes.

America's free-thinking, democratic, innovative and assertive global presence won't be snuffed out by one man.

Ensuring Trump can see things Australia's way might be an impossible task but making it in Trump's interests to be at least sympathetic to Australia's perspective is considered vital.

This is the strategy behind ambassador Joe Hockey's rejoinder about "100 years of mateship". It may appear twee, but it is calculated in its simplicity to lure Trump's jagged New Yorker scent for the straight player.

Trump, in business and in politics, has known few true friends. Australia offers its friendship unconditionally to the US.

But Australia's not stupid, nor anyone's lickspittle.

It knows that every unconditional friendship is paradoxically owed that little bit extra.

And this is the strategic gamble Scott Morrison plays, just as Turnbull did in skilfully ensuring Trump abided by Obama's promise to accept refugees from Nauru and Manus Island.

Riding two horses at once

Morrison needs Trump to not deepen hostilities with Xi, and instead resolve hostilities in the way that preserves existing global trade structure, not erode them.

That's easily said, but very hard to land when you're dealing with a man known to make foreign policy pronouncement by Twitter.

Tom Switzer, the executive director of the Centre for Independent Studies, predicts Trump will encourage Morrison to help contain China.

"But many people believe — understandably — that Donald Trump is not suitable to go shooting tiger with and there is a danger that if he miscalculates we could be caught in the crossfire," Switzer said.

He said Australia had done a very good job in recent years "riding two horses simultaneously", reconciling its biggest trade relationship with its most important security ally.

"All things considered, our leaders are doing the right thing finding that balance but we've got to be careful about not hopping on to any Cold War-style containment bandwagon," he said.

It's very unlikely Morrison would accede to any Trump treaty to contain China. It simply isn't in Australia's interests.

But constraining China might be something Australia would see as having virtue, if it helps slow South-East Asia's gravitational drift into Beijing's orbit.

Because constraining China using a strategic coalition of nations — say the US, Japan, Australia, India and another like-minded allies — would keep the Americans in the Indo-Pacific game and within existing, predicable rules of engagement too.

And that is what this trip is all about: a "mate" hoping the other starts seeing from his way of thinking.