Weeks before Prime Minister Justin Trudeau's quiet "pull-aside" at the UN laid the groundwork for a Canadian's release from an Iranian prison, Canada's foreign affairs minister was trying his own hand at corridor diplomacy — with his North Korean counterpart.

The subject of the brief meeting between Stéphane Dion and North Korean Foreign Minister Ri Yong Ho — the highest-level known contact between the two countries in years — was another Canadian imprisoned abroad.

Toronto-area pastor Hyeon Soo Lim was convicted last December in Pyongyang of plotting to overthrow the North Korean government using religious activity and is serving a life sentence in a hard labour prison camp. A family spokesperson has said Canadian officials who last visited him found his health had deteriorated.

Toronto-area pastor Hyeon Soo Lim, shown speaking during a news conference in Pyongyang on July 30, 2015, had taken humanitarian trips to North Korea more than 100 times. (Kyodo/Reuters)

There is no evidence that the previously undisclosed encounter between Dion and Ri on the margins of a multinational gathering back in July has made the slightest difference in Lim's case.

Well over two months later, he remains in prison.

Lim's supporters say Ottawa must engage at even higher levels to get results.

But given the delicate relations between the two countries — and between North Korea and most of the world — the encounter is still extraordinary.

CBC News learned it happened in Laos during a gathering of the Association of Southeast Asian Nations — or ASEAN — which Canada, as a partner, attended.

Unplanned and unscripted

Global Affairs Canada has largely avoided making public any details of any interventions on Lim's behalf, with officials citing the case's best interests.

Asked if there was a meeting, however, the department confirmed an encounter between the foreign ministers did take place, but that it was unplanned and unscripted: the two top diplomats had the exchange in a corridor after Dion approached and introduced himself.

"Minister Dion took the opportunity to raise an urgent consular matter with his counterpart," said Joseph Pickerill, a spokesman.

"It was very much a brief encounter about that urgent matter. He was able to raise it and then they parted ways."

Lim, centre, is escorted to his sentencing in Pyongyang, North Korea, on Dec. 16, 2015. (Jon Chol Jin/Associated Press)

Pickerill would not say what precisely was said or what requests Dion made, if any. Pickerill said the North Korean minister acknowledged Dion raising the issue but "no commitments were made."

Exactly six years ago this month, Canada imposed a policy of "controlled engagement" with Pyongyang in response to a pattern of "aggressive actions." It limits the Canadian government's interactions with Pyongyang to a handful of issues, one of which is addressing consular cases.

Even so, a minister-to-minister overture is highly unusual given the frosty relations.

While Canada recently made moves towards restoring relations with Iran — Dion recently met with its foreign minister, maintaining that engagement is more constructive than silence — there have been no public indications of such attempts with Pyongyang, one of the most isolated capitals on Earth.

Repeated calls

Last month, North Korea elicited worldwide condemnation for conducting its fifth nuclear test.

Lim's supporters have repeatedly called on the Canadian government to do more to secure his release.

They now point to the success of the prime minister's interventions in having Canadians Homa Hoodfar and Kevin Garrett released from Iranian and Chinese prisons as a model that can be used in Lim's case.

Lim started going to North Korea after he heard about famine and flooding problems in the country. (Light Korean Presbyterian Church)

"We know that in both cases the highest level of government officials, including Prime Minister Trudeau himself, were instrumental in the release of these fellow Canadians," Lim's Light Presbyterian Church said in a statement last week following Hoodfar's release.

"We urge the Canadian government to demonstrate the same attention and determination when engaging in diplomatic talks with the North Korean officials."

Others working on the case behind the scenes say only North Korean leader Kim Jong-un has the power to free Lim. They say Ottawa has been told repeatedly by those familiar with the case that high-level contact — beyond the foreign ministry — is the only way to achieve success in Lim's case.

Not so easy

Ottawa says it's not that simple.

While there are parallels with Iran — the fact that there is no diplomatic presence, for instance — Pickerill, Dion's spokesman, says North Korea and its leadership are unlike anyplace else, that the norm elsewhere does not necessarily apply.

We have to be very cautious. - Joseph Pickerill

"We're pursuing every avenue that we can and should, bearing in mind that with an unpredictable regime, not every approach necessarily reaches the outcome people might think," he said.

"So we have to be very cautious."

Canada has also discussed the matter with North Korea's neighbours, he added.

There are few countries with sway in Pyongyang — no real equivalent of Oman for Iran — with the exception of China, although even that relationship has recently been strained over the nuclear tests.

Lim, 62, the senior pastor of Light Korean Presbyterian Church in Mississauga, Ont., had travelled extensively to North Korea before being arrested in February 2015. Canadian consular officials last visited him in April.