NATO's secretary general has come out swinging in defence of the military alliance, and says Canada is playing a key role in helping to strengthen the 70-year-old organization thanks in part to its contributions to different missions.

In an interview with The Canadian Press, Jens Stoltenberg listed Canada's deployment of hundreds of troops to Latvia and Iraq, naval warships to NATO fleets and other assistance as critical to helping protect North America and Europe and strengthening the alliance's transatlantic bond.

"I'm extremely grateful for all the many contributions by Canada to the alliance, and by standing together, we are all safer," Stoltenberg said. "In an unpredictable world, we need strong multilateral institutions like NATO, and Canada is helping us to strengthen NATO."

From the outside, some might question just how strong the 29-member military alliance actually is as Stoltenberg joins Prime Minister Justin Trudeau and other NATO leaders here on Wednesday to officially mark its 70th birthday.

U.S. President Donald Trump and Prime Minister Justin Trudeau hold a meeting ahead of the NATO summit in London, on Tuesday. NATO's leaders formally meet Wednesday. (Kevin Lamarque/Reuters)

Sparks have been flying between U.S. President Donald Trump and his French counterpart, Emmanuel Macron, who have been at odds over the state of NATO, which was created at the start of the Cold War and is now facing new external threats and internal divisions.

Macron last month suggested the alliance was suffering from "brain death" because of a lack of co-ordination and communication between members, specifically Trump's surprise decision to pull U.S. troops from northeastern Syria.

'Canada is always helpful'

The U.S. president fired back Tuesday, calling Macron's words "nasty," criticizing France's economy and saying the European nation needs NATO more than the U.S. does. Macron refused to back down, calling for more focus from the alliance on strategic planning and less on money issues.

Trudeau has been among those leaders seeking to shore up alliance by underscoring NATO's importance to both North American and European security and its success at having ensured relative peace and security for its members since the end of the Second World War.

"Canada is playing an important role and Canada is always helpful to try to find ways forward when we see differences within this alliance," Stoltenberg said.

Leaders of the NATO alliance countries and its secretary general join Queen Elizabeth and Prince Charles for a group picture during a reception at Buckingham Palace in London on Tuesday. (Yui Mok/Associated Press)

"The strength of this alliance is ... we are 29 different nations from both sides of the Atlantic with different histories, different political parties and government, but despite these differences, we have always been able to unite around our core task to protect and defend each other.

'NATO is adapting'

At the same time, Stoltenberg said the alliance is changing to meet the threats of today and tomorrow. That includes not only a newly emergent Russia and, increasingly, China, but also domains like cyberspace and space itself as well as terrorism.

"So NATO is agile, NATO is adapting," he said. "We are adapting agilely in a time when we need to change because the world is changing."

Canada has had 600 troops leading a NATO battle group in Latvia since 2017. The battle group, which includes soldiers from eight other nations and is one of four such forces in the Baltics and Poland, was established in reaction to Russia's annexation of Ukraine's Crimea peninsula.

The federal government has said Canada will continue to lead the battle group until at least 2023. Asked how long Canadians could be required as a check against Russia, Stoltenberg said: "I will not speculate about how long. This is a presence which doesn't have a specific time limit.

"So far it's very hard to say there are positive signs," he said of Russia. "But we need to continue to work and to strive for progress because this is in our interests to find ways to prevent a new Cold War and to prevent a new arms race."

If there is one positive in the West's tense relationship with Russia, however, Stoltenberg suggested it is that Canada and the U.S., which is leading a battle group in Poland, have stepped up to once again help Europe in a time of need.

"I can hardly think of any stronger demonstration of North America's commitment to NATO and to European security than more Canadian and U.S. troops in Europe."