Republican presidential nominee former U.S. President Donald Trump points to the crowd at an election night watch party, in West Palm Beach, Fla., U.S., Nov. 6. AP-Yonhap

A turbulent new chapter seems to have begun for the South Korea-U.S. alliance with Donald Trump's potential return to the White House, as he nears victory in the U.S. presidential election.

Analysts warn that the Republican candidate's "Make America Great Again" policy could once again test the decades-old Seoul-Washington alliance, recalling the turbulence witnessed during his previous term from 2017 to 2021.

During his previous term, Trump demanded a substantial increase in Seoul's financial contribution to support U.S. Forces Korea (USFK). In his current campaign, he referred to South Korea as a "money machine" while discussing defense cost-sharing, indicating that his position on the issue remains firm.

However, with the U.S. currently focused on major international concerns like the war in Ukraine and the Middle East conflict, some analysts suggest that any drastic policy shifts regarding the Korean Peninsula under a Trump administration might be postponed. Nevertheless, given Trump's often unpredictable approach to foreign policy, these expectations could be upended.

Then-U.S. President Donald Trump, left, talks with then-President Moon Jae-in at the Korean Demilitarized Zone from Observation Post Ouellette at Camp Bonifas in South Korea, in this July 2, 2019 file photo. AP-Yonhap

The Yoon Suk Yeol administration, which prioritizes bolstering its alliance with the U.S. against North Korean threats, is likely to face fresh challenges as Trump may dismantle major security initiatives established by President Joe Biden.

"I would assume that Trump will seek to discontinue several key initiatives launched under Biden, and that could include the Nuclear Consultative Group (NCG)," said Ramon Pacheco Pardo, professor of international relations at King's College London.

"After all, the NCG may seem beneficial to South Korea but not to the U.S. from a 'Trumpian' conception of alliances," he added.

Harry Kazianis, senior director of National Security Affairs at the Center for the National Interest, echoed that view.

"Trump might just see it (NCG) as a talking shop that does nothing and kill it off," he said.

The NCG was established under the Washington Declaration signed by Yoon and Biden during the South Korean president's U.S. visit in April 2023. The joint initiative was aimed at enhancing U.S. extended deterrence commitments to South Korea in response to North Korea's nuclear threats.

If Trump weakens the NCG or the U.S. nuclear umbrella, it may intensify calls in South Korea to develop its own nuclear weapons. This is an approach Trump could potentially support.

In South Korea, there is a growing push for self-nuclear armament, driven by increasing skepticism over the effectiveness of U.S. assurances in deterring North Korea's nuclear threats.

"I would not be shocked if Trump greenlighted South Korea building nuclear weapons — he might even encourage such a move out in the open for a lot of reasons," Kazianis said. "He could be of the mindset that it's unfair for North Korea to have these weapons and not South Korea."

Kazianis suggested that a nuclear-armed South Korea might appeal to Trump, as it would allow the U.S. to focus resources on countering China, while South Korea can shoulder more responsibility for deterring North Korea. This could even pave the way for Trump to scale down the presence of USFK on the peninsula, based on the notion that South Korea could deter Pyongyang independently.

U.S. Forces Korea members participate in a military parade in central Seoul to mark the 76th anniversary of the Armed Forces Day, Oct. 1. Yonhap

Another potential strain on the bilateral alliance is Trump's stance on increasing South Korea's share of the cost to station USFK troops.

In October, South Korea and the U.S. finalized the 12th Special Measures Agreement (SMA), which outlines Seoul's financial obligations for hosting 28,500 USFK troops. Under this agreement, South Korea will contribute 1.52 trillion won in 2026, marking an 8.3 percent increase from 2025.

After the deal was struck, Trump claimed that Seoul would have paid $10 billion annually if he were president.

Sean King, senior vice president at Park Strategies, a New York-based consulting firm, viewed that Trump may revisit the newly-signed SMA.

"Trump would look to redo it just like he renegotiated the (South) Korea-U.S. Free Trade Agreement (KORUS FTA). If Trump wins, everything's up for renegotiation or review," King said.

Lim Eun-jung, a professor of international studies at Kongju National University, pointed out that while Trump might aim to reshape the alliance to fit his own style, the Korean Peninsula may not be a top priority for him when he assumes office.

"In the immediate term, Trump is expected to focus on the Ukraine war, Middle Eastern conflicts and domestic priorities, which could give South Korean officials time to prepare for potential curveballs the Trump administration may throw," she said.

While some see Trump's return as a major threat to the South Korea-U.S. alliance, Lim suggested it could also bring unexpected opportunities, especially in terms of the ongoing stalemate between the two Koreas.

"There has been growing discontent here about the U.S. Democrats' status-quo approach on North Korea, during which the regime advanced its nuclear capabilities. A new Trump era could bring unexpected shifts, although this unpredictability might be challenging for South Korean officials to navigate," she said.

President Yoon Suk Yeol, U.S. President Joe Biden and former Japanese Prime Minister Fumio Kishida pose during a trilateral summit at Camp David, the U.S. presidential retreat, near Thurmont, Md., Aug. 19, 2023. AP-Yonhap

However, maintaining the South Korea-U.S.-Japan trilateral framework could be one of the few aspects of America's Asia policy that Trump carries over from the previous administration. The Biden administration emphasized strengthening ties among the three allies to address common security threats in the region, particularly those posed by North Korea and China's rising influence.

Although Trump prioritizes bilateral dealings over multilateral frameworks, the Seoul-Washington-Tokyo security partnership could be instrumental in containing Beijing, which he views as an existential threat, according to Kazianis.

But sustaining the trilateral framework could come at a higher cost for Seoul and Tokyo.

"I don't think that Trump would be as willing to spearhead trilateral leader summits or other high-level meetings. I also believe that he would ask South Korea and Japan to shoulder a greater share of the cost of trilateral cooperation," Pacheco Pardo said.