HALIFAX -- Views differed sharply on the impact of Donald Trump's presidency on issues from trade to historic alliances during the second day of an international gathering seized by what-if scenarios regarding the incoming U.S. administration.

The Halifax International Security Forum is the first major international gathering of policy analysts, American and foreign politicians, and defence ministers since Trump won the U.S. election.

Gideon Rose, editor of Foreign Affairs, added a touch of humour to the proceedings Saturday when he crumpled up a piece of paper with his seminar's original title on it, suggesting it was already dated by the Trump topic.

However, Rose also said the topics under discussion -- such as Trump's statements during primary debates that he favours waterboarding torture -- are new to the forum on democracy.

"Let me say how appalling and heartbreaking it is that we have to have a discussion about the possibility ... about whether the United States policy really will be not to engage in war crimes," he said.

During the same panel, Francois Heisbourg, chair of the International Institute for Strategic Studies in London, jumped on Trump's election comments suggesting his support for defending NATO members depends on their military spending.

The London-based analyst said this musing during the campaign is already creating divisions in decades-old alliances with European nations and could create a stampede towards isolationism.

"The uncertainty has already been created," said the policy analyst. "And once you do that it's doubtful this alliance system can actually be sustained as this basic given."

Some Republican legislators attending seemed to support Trump, yet simultaneously raise opposition to some of his specific policy ideas.

"I believe there's every opportunity for us to work together," said the Senator John McCain, the chair of the armed services committee, during an interview with one of the moderators.

Yet, he also differed with the president elect's campaign positions on everything from reworking the North American Free Trade Agreement to cosying up with Russian President Vladimir Putin in Syria.

Regarding Trump's threat to renew waterboarding torture, McCain noted that the American congress has already passed a bill that prohibits it.

"I don't give a damn what the president of United States wants to do or anybody else wants to do, we will not waterboard," he said.

Though he stopped short of explicitly supporting the existing North American Free Trade Agreement, McCain warned that previous bouts of protectionism contributed to the Great Depression.

He also said if the United States doesn't ratify the Trans Pacific Partnership -- as Trump has made clear -- it will lead China to expand its sphere of influence in the Far East.

Meanwhile, in a separate panel on Asia, Alaska Republican Sen. Dan Sullivan recalled many Americans see Trump's election as "an opportunity" to improve the country's economy after years of stagnation.

"If this president can unleash traditional levels of American gross domestic product growth, that's going to be a game changer," he said.

Sullivan also said he expects under the U.S. government under Trump will allow more oil exploration off his state's pristine coastlines.

Delaware Sen. Chris Coons, a democrat who referred to Trump as a "vulgarian" during the campaign, said he expects American legislators can deter the president elect from pursuing policies that ultimately damage his country's interests.

Coons said the main reason there is a large bipartisan delegation from the congress at the forum is to reassure Canadians and representatives from 70 countries that fundamental American values, priorities and security commitments won't change.

"I've been encouraged by the more steady tone president elect Trump has taken since his election," he said during an interview.

However, as discussions unfolded, some commentators said it's also essential for Western allies to keep a close watch on what Trump does, and for legislators to map out strategies of resistance.

Rosa Brooks, the associate dean for graduate studies at Georgetown University in Washington, said during a panel discussion that Trump's opponents must prepare carefully and not give up.

"I'm scared ... some of the things said on the campaign trail were terrifying," she said.

She said it's naive to assume "president Trump will go through a personal transformation and ideology transformation."

"It's equally bad to assume it's all over we've lost every fight already and we might as well resign or ask our nice Canadian friends here to let us stay."

Rose said the forum is fulfilling its purpose by making clear to the new administrator the world is watching.

"I really hope when we look back on this in later years ... we will look at this period and say, 'we dodged a bullet' but until that happens I make no apologies for raising and discussing all of this uncertainty," said the editor of Foreign Affairs.