Canada's deeply entrenched role in the fight against global extremism is more focused these days on intelligence-gathering — and sharing — than on putting more boots on the ground in the Middle East, Justin Trudeau suggested Thursday.

"The track record has shown that collaboration and co-operation between allies, friends and partners has saved lives and keeps all of our citizens safe," Trudeau said at the outset of a day-long NATO meeting in Brussels.

"We are going to continue to collaborate and to work together to ensure we're doing everything we can to keep citizens and our communities safe."

Trudeau brushed aside concerns that NATO's agreement to increase intelligence-sharing in the fight against terrorism comes amid accusations that President Donald Trump and others in the U.S. are playing fast and loose with sensitive secrets.

The White House has come under fire in recent days over revelations that Trump shared Israeli intelligence in a meeting with Russian Foreign Minister Sergey Lavrov. And the British government assailed U.S. officials for leaking sensitive details and crime-scene photos from the investigation into Monday's deadly terrorist attack in Manchester.

Trump issued a statement Thursday saying the White House intends to get to the bottom of what he called "deeply troubling" leaks.

"The leaks of sensitive information pose a grave threat to our national security," the statement said.

The North Atlantic Treaty Organization leaders spent Thursday hunkered down inside the sparkling new Brussels headquarters to discuss how they can better co-ordinate efforts in the fight against terrorism — and better share the cost of defence.

The decision to zero in on those two major priorities were part of an effort to woo Trump, whose country is a driving force behind the military alliance - a body he described as "obsolete" during last year's election campaign.

One big source of anxiety among the allies was the Trump had never explicitly endorsed Article 5 - the self-defence clause that means an attack on one member generates a response by all.

U.S. President Donald Trump was greeted by European Council President Donald Tusk, left, as he arrived for a meeting between American and European Union officials. This week's NATO meetings are Trump's first since taking office. (Olivier Matthys/Associated Press)

Fighting terrorism

The calls for unity — and a strong alliance — were coming fast and furious from various leaders throughout the day, with Belgian Prime Minister Charles Michel laying it on particularly thick during a ceremony to inaugurate the new building.

"Our common values are not obsolete," Michel said, as Trump sat behind him with his fellow leaders, his arms crossed.

Trump appeared, in his way, to try to put those fears to rest as he dedicated a monument commemorating how NATO came to the defence of the U.S. after 9/11.

"We will never forsake the friends who stood by our side," Trump said.

Kate Purchase, director of communications for Trudeau, said Trump delivered a similar reassurance in the room.

"I think he actually did make a commitment to the NATO table," she said.

Still, Trump decided to make the fight against terrorism a central focus of his public remarks.

"All people who cherish life must unite in finding, exposing and removing these killers and extremists, and yes, losers," said Trump. "They are losers. Wherever they exist in our societies, we must drive them out and never, ever let them back in."

To that end, NATO Sec.-Gen. Jens Stoltenberg announced the alliance would be formally joining the U.S.-led coalition against the Islamic State of Iraq and the Levant, albeit without a role in combat operations.

"NATO joining the coalition to defeat (ISIS) is a strong political message of unity in the fight against terrorism," Stoltenberg said.

All 28 NATO allies, including Canada, are already part of the anti-ISIS coalition, and the military alliance has been involved in training Iraqi forces. Still, Trump had been urging the alliance to take on a bigger role.

Chief of Defence Staff Jonathan Vance, left, and Defence Minister Harjit Sajjan, beside Vance, are with Trudeau at the NATO Summit. Trudeau told reporters that Canada's underfunded troops are a priority for his government. (David Cochrane/CBC News)

NATO also agreed to assess its "level of support and the future of the mission" in Afghanistan, but Trudeau betrayed no enthusiasm for sending soldiers back.

"We have no troops in Afghanistan at this time, but we are happy to be supportive in other ways."

Trump has also been vocal in his demand for the other members of NATO to pick up their fair share of the tab when it comes to defence spending, urging members to meet their commitment to ramp up their contributions to two per cent of GDP.

Canada spends just over one per cent of its GDP on defence.

His government's much-anticipated defence policy will be released in two weeks, Trudeau confirmed, defending not having the Liberals' revised plans for the military ready in time for this summit by saying officials have "taken the time to get this right."

The Liberal government says its contribution is bigger than the numbers suggest, citing its commitment to send up to 455 troops to head up a multinational mission in Latvia, as part of efforts to curb Russian aggression in the Baltics.

"All our allies understand that Canada has always been there, and I can assure them — and I will continue to assure them — that Canada will continue to be there," Trudeau said.

Purchase said Trudeau delivered a similar message when it was his time to speak during the working dinner, while at the same time urging every NATO member to step up.

She said it was received positively.

"Not a single (leader) had a negative thing to say about Canada's contribution to NATO," Purchase told reporters travelling with Trudeau while aboard the flight to Taormina, Sicily, for the G7 Summit.

She said that included Trump.

"He gave him a big thumb's up," Purchase said.