Donald Trump may prove to be Prime Minister Justin Trudeau’s biggest challenge in office yet, Canada’s former foreign affairs minister says.

Lloyd Axworthy says the U.S. president-elect will be “perhaps the most significant roadblock” Trudeau will have to deal with in office.

Axworthy said Trump represents a “total contradiction” to what most Canadians believe and says that’s going to put the rookie prime minister in a tough spot going forward.

“They’re going to have to reconcile very distinct and opposite directions and values, in effect, that the two countries have,” said Axworthy, a former federal Liberal foreign affairs minister and past president of the University of Winnipeg.

“He’s got a very tough balancing act.”

Axworthy said issues about the environment are likely to be a sticking point for the two sides, especially if Trump pulls out of the Paris Agreement.

New allies needed

Trudeau will have to cultivate other supporters of the climate change agreement, he said.

“I think he’s really going to have to find other key allies,” Axworthy said, adding Germany could soon become a key partner for Canada, representing a shift on the world stage.

“We may be one of their best North Americans partners to work on,” Axworthy said.

Trudeau congratulated Trump about his election to office earlier this week and promised to work with the soon-to-be president on issues around trade and security.

Trudeau said Canada’s relationship with the U.S. is based on shared beliefs and the two countries will always remain allies.

Meanwhile, Axworthy said he is still in disbelief about Trump’s impending term in the Oval Office.

“It’s still hard observing those exact words,” he said of the president-elect’s title.

“One of the most senior of President Clinton’s former administration that I’ve worked with over the years was suggesting that maybe I should get the guest room ready at least for extended visits if not for full occupancy,” he added.