Prime Minister Justin Trudeau's first face-to-face meeting with U.S. President Donald Trump on Monday will set the tone for their relationship, former diplomats are advising him.

But, even with so much riding on that meeting, America's former ambassador to Canada says Trudeau shouldn't focus on the risks.

"I wouldn't worry about the dangers. I think it's an opportunity," Bruce Heyman, who left Ottawa last month, said in an interview with Evan Solomon, host of CTV's Question Period. The interview will air Sunday.

"The opportunity is to come in and build rapport with your next-door neighbour, your largest trading partner, your ally.... These two men will have a lot to work together on, for prosperity for both Canadians and Americans, and for protection. And those are the things that both a prime minister and a president have as an obligation to the people: prosperity and protection."

Early-stage meetings between a president and other world leaders allow them to establish a personal rapport regardless of political philosophy, Heyman said.

"Once there's this understanding that we protect North America together, through NORAD and NATO ... this is readily apparent: that the Canadian relationship is one of the -- if not the most -- important relationship the U.S. has in the world," he said.

"There are a lot of paths forward here."

Former Canadian ambassador to the U.S. Derek Burney, who has spoken with members of Trudeau's team about relations with the Americans, advises the prime minister to keep calm and try to detect the underlying reasons for the positions Trump takes during their meeting.

"Trump has got two major priorities as far as I'm concerned: economic growth and physical security. There's no other country in the world that can work better with him on those two objectives than Canada. That would be the message I would be conveying," Burney told Solomon.

"The objective for the prime minister in a first meeting of this kind is to set the tone for a personal relationship that can produce dividends, not confrontation."

That said, Canadian officials shouldn't hesitate to raise areas of disagreement in private meetings with the Americans. But those shouldn't be the focus, Burney said.

"If we put the emphasis on the things that we disagree about, then we'll have a disagreeable meeting. And don't get me wrong -- there are areas in which we have fundamental differences with the Americans and we shouldn't be hesitant to express those in private, in a polite, professional manner. It's a difference between private frank discussion and grandstanding. We've got to avoid saying things in public that were not said during the meeting."

Burney says the two leaders aren't likely to make any kind of breakthrough on substance since Trump doesn't yet have his team in place. For example, Commerce Secretary Wilbur Ross hasn't been confirmed yet.

"I really think this will enable the two leaders to come together as people and decide whether this is a relationship on a personal level they want to sustain, and then go into substance [later]," Burney said.

Former media baron Conrad Black, a friend of Trump's, says Trudeau can ease the relationship if he is open to increasing defence spending to two per cent of GDP, something to which Canada committed as a NATO member and an issue former U.S. president Barack Obama raised during his visit to Ottawa last year.

"If Justin can say something to the effect that we'll move in that direction over the next couple of years, that will be a real plus point. And incidentally, they are both very charming, personable people. They'll get on like smoke, I think," Black said.