Former U.S. President Donald Trump, right, poses with North Korean leader Kim Jong-un during their first summit in Singapore in June 2018. The encounter led to the Singapore Agreement, marking the first time a sitting U.S. president met with a North Korean leader. The agreement outlined commitments from both countries to improve bilateral relations and work toward the denuclearization of the Korean Peninsula. Yonhap

As U.S. President-elect Donald Trump prepares for his second term, uncertainties loom over the Korean Peninsula, already fraught with North Korea's nuclear threats. South Koreans are increasingly anxious about the potential return of Trump's unpredictable diplomatic approach.

Many South Koreans recall the "roller-coaster diplomacy" of Trump's first term, marked by fiery exchanges with North Korean leader Kim Jong-un, followed by three high-profile meetings. Despite these encounters, negotiations ultimately failed, leaving the nuclear issue unresolved and even more complex.

Trump's second term could introduce new uncertainties to the region. The North Korean leader might view this as an opportunity to improve relations amid heightened nuclear tensions.

Cheong Seong-chang, a senior fellow at the Sejong Institute think tank, estimates a 51 percent chance of dialogue resuming. He emphasized that the success of such summits would heavily depend on the U.S. approach.

"During Trump's first term, his administration lacked a systematic negotiation strategy, leading to unrealistic demands such as asking North Korea to disclose its nuclear program or provide a list of its nuclear assets," Cheong said.

To avoid repeating these mistakes, he stressed the need for capable strategists in both the Trump administration and the South Korean government to support U.S.-North Korea negotiations. "While a summit might be held, its chances of success appear to be quite low," Cheong added.

Cheong also highlighted North Korea's primary demands: the suspension of U.S.-South Korea joint military exercises and sanctions relief.

"North Korea's main demand is the suspension of U.S.-South Korea joint military exercises, which the U.S. will find hard to accept," he said. "However, Trump's second administration is likely to appoint loyalists who will implement his directives without question, increasing the possibility of a U.S.-North Korea compromise compared to the first term."

Speculation is growing that Trump's renewed presidency might bring significant changes. Some believe he could leverage the withdrawal or reduction of U.S. troops in South Korea to pressure for a substantial increase in defense cost-sharing. There's also the possibility of rekindling his personal rapport with Kim Jong-un.

If this happens, experts believe North Korea would return to negotiations with much stronger leverage, having significantly advanced its nuclear and ballistic missile capabilities since Trump's first term.

If talks resume, experts suggest that North Korea's demands would also likely focus on limiting rather than eliminating nuclear weapons, diverging from the U.S. and its allies' long-standing goal of complete, verifiable and irreversible denuclearization.

Yang Moo-jin, president of the University of North Korean Studies, identified the primary concern as the agenda for any potential talks.

"Our primary concern will likely be the agenda. From North Korea's perspective, over the six years since 2018, its nuclear capabilities have advanced, and inter-Korean relations have become more hostile, transforming into two adversarial states," he said. "Based on this, North Korea might push for nuclear arms reduction talks. However, from Trump's side, they might argue against nuclear arms reduction talks and instead propose returning to the spirit of the Singapore Agreement."

Yang highlighted the achievements from previous engagements between the two countries, emphasizing the significance of the Singapore Agreement on June 12, 2018. This agreement marked the first time a sitting U.S. president met with a North Korean leader, outlining mutual commitments to improve bilateral relations and work toward the denuclearization of the Korean Peninsula.

"There were achievements, and how we set the criteria for those achievements matters," Yang said. "For instance, the Singapore Agreement was a significant outcome. Following that, there were ongoing negotiations between working-level officials from North Korea and the United States. During that period, nuclear tests and ICBM (intercontinental ballistic missile) tests by North Korea, as well as joint military exercises involving strategic assets between the U.S. and South Korea, were suspended."