Stephen Biegun, former US deputy secretary of state and top nuclear negotiator, speaks during a forum hosted by The Korea Society on Tuesday. (YouTube account of The Korea Society)

A former US deputy secretary of state expected Tuesday that it won't take "long" for North Korea's security quandary to begin moving toward the top of the policy agenda for the incoming Trump administration as the recalcitrant regime could otherwise explore ways to draw attention.

Stephen Biegun, who served as the State Department's No. 2 official and top nuclear envoy during the first Trump administration, made the remarks amid expectations that President-elect Donald Trump could seek to revive his personal diplomacy with North Korean leader Kim Jong-un after his inauguration in January.

"I don't expect this (North Korean) issue to sit long before it begins to percolate towards the top of the agenda," he said during a forum hosted by The Korea Society.

"And if it doesn't, then I expect the North Koreans might themselves look for ways to make sure it does, which is often the case," he added.

On the stump, Trump had boasted about his personal relations with Kim and his receipt of "love letters" from the reclusive leader, spawning speculation that he could seek to complete the unfinished business of addressing North Korea's nuclear conundrum.

During his first term, Trump employed a direct leader-to-leader approach to the North, leading to three in-person meetings with Kim, including the first-ever bilateral summit in Singapore in 2018, though serious nuclear talks have been stalled since the no-deal summit in Hanoi in February 2019.

"I do think there will be some engagements," Biegun said. "It's not the top priority ... although (Trump) has addressed it even in the course of the campaign with some references to North Korea and to his personal like for Kim Jong-un that wouldn't have been lost on the North Koreans either."

He pointed out a series of changes in the environment that the next set of US negotiators will face for diplomacy with Pyongyang.

"Of course, the geopolitical tensions, the war in Ukraine, the presence of North Korean troops outside the Korean Peninsula -- to my knowledge for the first time ever certainly at this scale," he said. "There are a lot of implications for those things, both for North Korean interests and for North Korea's policies and for US interests as well."

Touching on the North's troop deployment to Russia, Biegun warned North Korea about the "full" consequences and the "lasting" effect of the troop dispatch, stressing that North Korea is "in uncharted territory."

"This is fundamentally contradictory to juche. This attacks the foundational philosophy that the North Korean regime has used to rationalize its dictatorship for decades," he said, referring to the North's long-cherished ideology of juche or self-reliance.

"North Korea is now dependent upon Russia for aid and for technology in ways that it was loath to be in the past, and North Korea has extended itself outside its hermit kingdom, outside its traditional isolated orbit, to send its troops into a foreign conflict for the first time since 1948."

He went on to say that by joining the conflict, Pyongyang is exposing itself to "geopolitical forces that they have never had to contend with before."

"Some will be advantageous to them. They have a partner in Russia now that they can depend upon. They have a counterweight to China if they need it. And they have a counterweight to us as well," he said.

"But they also have essentially declared war against a country -- Ukraine which is in an existential battle for its sovereignty and independence."

Biegun highlighted the importance of maintaining the denuclearization goal in negotiations with North Korea rather than shifting toward "arms control" with the regime.

"Even if de facto, any negotiation that we have with the North Koreans leads to a very long process of denuclearization, the end state that both sides have to agree to is denuclearization," he said.

"Otherwise, there are secondary and tertiary interests that we have, that will be deeply affected. If we legitimize and accept North Korea as a nuclear weapons state, we are risking unleashing a round of nuclear proliferation which I believe will not end with North Korea."

During his term as America's point man on North Korea, he had heavily engaged in diplomacy with North Korea, including preparations for the 2019 Hanoi summit.

Currently, Biegun is senior vice president of global public policy at The Boeing Company. (Yonhap)