Canada is looking to Trump-proof its arguments on a range of defence issues ahead of next month's NATO summit — but some experts wonder whether the Trudeau government's position will even register with the mercurial U.S. president.

Defence Minister Harjit Sajjan signalled the Liberal government is prepared to debate the orthodoxy of the western military alliance's non-binding spending targets at the upcoming NATO leaders summit in Brussels.

NATO asks its 29 members to spend the equivalent of two per cent of their gross domestic product on defence.

Canada has long been singled out as a laggard when it comes to meeting that target. Sajjan contends it's partly because the federal government is too bashful when it comes to what it describes as defence spending.

"We've been too Canadian in how we calculate our two per cent compared to other nations," Sajjan told CBC News in a recent interview.

"We're always too modest. When I looked at the calculation, I looked at how some nations add certain things that we haven't."

First Trudeau-Trump meeting since the G7 debacle

The remarks are significant in light of a recent letter U.S. President Donald Trump sent to all NATO capitals demanding members meet the alliance's defence spending targets.

Sajjan's comments come at a low point in Canada-U.S. relations. The working relationship between Prime Minister Justin Trudeau and Trump has turned frosty since the president started calling out Canada — and Trudeau himself — on social media and in highly emotive political rallies with supporters.

The NATO summit is expected to be the first time the two leaders have met since the G7 in early June, where the U.S. president backed out of supporting the final communique and launched blistering personal attacks on Trudeau in response to the prime minister telling the international media that Canada would not be "pushed around" by the United States on trade.

The possibility of a repeat performance by Trump in Brussels has the Liberal government sharpening its previous arguments on defence spending.

"How the two per cent is calculated needs to be looked at," Sajjan said. "Now, we've done that and we look forward to talking more about that at the leaders summit."

As part of its recent defence policy, the Liberal government said Canada was not reporting certain expenses as defence spending — direct payments to veterans, defence procurement costs and bills not covered by the UN for peacekeeping operations, among other things.

The plan pledged to increase the defence budget to $32 billion per year by 2026-27. That boost still only brings Canada's defence spending to 1.4 per cent of GDP.

Sajjan has long argued the debate should not be about cash but rather "how you contribute to NATO" in terms of deployments — a position the former Conservative government also took when it was challenged on the issue.

He downplayed the suggestion that Canada was trying to tranquilize Trump with arguments about the structure of the two per cent target and burden-sharing.

"This is not about adding things on to appease somebody. This is about being effective together as NATO," he said.

Using facts and citing this country's recent defence policy to head off a potential Trump tirade might not work, a trio of experts has concluded.

"Mr. Trump is probably unaware of the 'fully costed' spending projections in the 2017 Canadian defence policy statement, Strong, Secure, Engaged – and, even if he was, his mind is probably made up anyway," said Christian Leuprecht, Joel Sokolsky and Jayson Derow in a report written for the MacDonald-Laurier Institute, released Monday.

A political bonus for Trudeau?

They argue there could even be a domestic political upside for Trudeau in resisting American pressure to put more money than planned into defence.

"To be sure, the prime minister could surge defence spending, but it is not clear Trump would take notice, let alone be satisfied with whatever Canada could reasonably inject, especially given the federal government's highly fiscally constrained environment," said the report, which examines Canada's commitment to NATO's battle group in Latvia.

"To the contrary, the Prime Minister may well decide that Trump's recent imposition of tariffs on some Canadian goods and his disparaging ad hominem remarks gives him licence and domestic support to resist U.S. pressure to ramp up defence spending."

Other defence experts have for years argued the two per cent benchmark is a poor way to measure a nation's contribution to the NATO alliance.

The benchmark was conceived at the Prague Summit in 2002 as a mechanism for members to pay their fair share, and reaffirmed four years later when leaders met in Riga.

The basis of the Canadian argument is that the spending target focuses on "inputs rather than outputs."

Washington has signalled already that it is going into the upcoming summit with the goal of pushing the alliance to keep more forces combat-ready.

The proposal, known as the 'Four Thirties', demands that within two years NATO be able to deploy 30 battalions, 30 warships and 30 air squadrons within 30 days or less.

At the Riga summit in 2006, NATO leaders introduced a target of maintaining 40 per cent of NATO land forces to be deployable on a sustained basis.

All alliance countries, with the exception of Denmark, keep their readiness statistics a secret.

Canada's top military commander, Gen. Jonathan Vance, recently described the Four Thirties concept as "a very interesting, useful proposal," but was uncertain of its impact on this country.