BRUSSELS -- 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.

Their main motivation, though, was 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.

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 (ISIL) 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-ISIL 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.

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.

Earlier, the U.S. president made the fight against terrorism the central focus of his speech as he dedicated a monument commemorating the invocation of Article 5 -- the self-defence clause that means an attack on one member generates a response by all.

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

Trudeau suggested the role that Canada now plays in fighting terrorism is through its membership in the so-called Five Eyes, an intelligence-sharing alliance that also includes the U.S., the U.K., Australia and New Zealand.

"We continue to be an important and trusted ally in the global intelligence community," said Trudeau, who noted he would not go into detail.

"There are many, many occasions upon which we have directly participated and in other occasions directly benefited form information-sharing between security agencies and at the highest level."

And while NATO agreed to assess its "level of support and the future of the mission" in Afghanistan, 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 about his demand for the other members of NATO to pick up their fair share of the tab when it comes to defence spending. Canada spends just over one per cent of its GDP on defence, just half of NATO's target.

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.

Stoltenberg, for his part, appeared to indicate some sympathy for the Canadian position.

"This is not just about cash, but also modern capabilities and meaningful contributions to NATO's missions, operations and engagements," he said. "Today, we will take steps to keep up the momentum."