SEOUL — Four months into his new administration, President Yoon Suk-yeol of South Korea has found himself in trouble.
His national approval rating has plummeted, his governing People Power Party does not control Parliament and five of his cabinet-level appointees have been forced to step down amid accusations of nepotism, sexual harassment and other ethical lapses.
Yet despite myriad domestic challenges, Mr. Yoon is hoping to boost his popularity at home and raise his profile on the world stage by pursuing a new foreign policy agenda that would deepen his country’s alliance with Washington in everything from missile defense to global supply chains while seeking not to antagonize China or provoke North Korea into war.
In an interview with The New York Times on Wednesday, the South Korean president said it had become necessary — even inevitable — for Seoul to expand its security cooperation with Washington and Tokyo as North Korea intensified its nuclear threat.
Executing such a policy will be a painstaking balancing act for Mr. Yoon. All of his recent predecessors have tried and failed to roll back the North’s nuclear program. And none have faced the geopolitical headwinds posed by the intensifying rivalry between the United States, South Korea’s main security ally, and China, its biggest trading partner and a friend to North Korea, quite like Mr. Yoon.
Mr. Yoon was careful in the interview to point out that his country’s security partnerships were not aimed at China. “Our defense system is to deal with the North Korean threat, not China or other countries,” he said.
On Tuesday at the United Nations General Assembly, he is scheduled to deliver an address in which he is expected to emphasize his country’s commitment to the “rules-based international order,” a mantra frequently repeated by top American diplomats like Secretary of State Antony J. Blinken.
Mr. Yoon, 61, would seem an unlikely candidate to achieve a diplomatic breakthrough. In his office, he had framed photos of stray dogs that he and his wife, Kim Keon-hee, adopted. (To the couple, who have no children, the pets are “more than a family,” his aides said.) On his desk was a plaque that read “The Buck Stops Here,” a gift from President Biden when he came to Seoul in May.
Before winning the presidential election with a razor-thin margin in March, Mr. Yoon had been a prosecutor for 26 years and never held elected office. Critics cited his lack of experience as a liability for South Korea.
But the president sounded determined to reverse the foreign policy decisions made by his progressive predecessor, Moon Jae-in, who helped arrange the historic summits between Kim Jong-un, the leader of North Korea, and former President Donald J. Trump.
Mr. Kim and Mr. Trump failed to reach a nuclear disarmament deal during the meetings. Since their diplomacy collapsed, North Korea has continued to develop its weapons program while international sanctions have crippled the country’s economy. Mr. Yoon has called meetings Mr. Moon held with Mr. Kim a “political show.”
He leaned forward during the interview as he compared Mr. Moon to a “student obsessed with only one friend in his classroom: North Korea.” He also criticized Mr. Moon’s stance between the United States and China, calling it too ambiguous.
“I will pursue predictability, and South Korea will take a more clear position with respect to U.S.-China relations,” he said.
As part of those efforts, he has built up his credentials among South Korean conservatives by reinstating the joint U.S.-South Korean military exercises which were canceled or downsized under Mr. Moon and Mr. Trump.
Under Mr. Yoon, South Korea joined the Indo-Pacific Economic Framework, often seen as an American-led effort to counter China in the race to secure global supply chains. He also agreed to attend preliminary talks for a technology alliance known as “Chip 4” with the United States, Japan and Taiwan.
Despite fears that doing so could anger China, Mr. Yoon said that it was “necessary” for the four nations to cooperate more closely.
His intentions of aligning his country more firmly with the West were made especially clear in June when he became the first South Korean president to attend a NATO summit.
“If one country tries to change the current territorial status with force, all countries should stand in solidarity to deter such kind of aggression,” Mr. Yoon told The Times in an apparent reference to Russia’s invasion of Ukraine.
He has also been hard at work trying to mend fractured bilateral ties with Japan, a long-running headache for Washington. He said he hoped to strike a “grand bargain” with Tokyo over thorny historical issues that have kept South Korea and Japan, the country’s former colonial ruler, barely on speaking terms.
Park Won-gon, a political scientist at Ewha Womans University in Seoul, said, “Unlike Moon Jae-in, whose focus was pretty much on inter-Korean relations and within the Korean Peninsula, Yoon pursues values-based internationalism and seeks to deal with the North Korea issue under that frame.”
Mr. Yoon said Seoul and Washington were prepared to bring “a package of all possible means and methods,” including the American nuclear umbrella, to bear on North Korea to avoid a war. But he also wanted Mr. Kim to know that a bright economic future awaited his people if he chose denuclearization.
Mr. Yoon’s pursuit of diplomacy in tandem with the Biden administration collides with the reality of South Korea’s interlocking trade ties with China, said Cheong Seong-chang, a senior analyst at the Sejong Institute, a think tank in South Korea.
“President Yoon lacks a clear and detailed direction because South Korea cannot ignore China,” he said.
So far, Mr. Yoon has challenged Beijing on a number of fronts. He declared that he didn’t feel bound by Mr. Moon’s “three-no” policy, which stated that there would be no additional deployments of an advanced American missile defense system known as Thaad in South Korea, no participation in the U.S. missile defense network and no trilateral military alliance with Washington and Tokyo.
China has called Thaad a threat to its security and retaliated economically against South Korea after the country’s first Thaad deployment in 2017. Mr. Yoon said the Thaad deployment was vital to South Korea’s defense against the North. “It is a matter of sovereignty and security, which is not subject to any compromise,” he said.
Still, the president tacitly acknowledged that there were limits to how far South Korea could go in confronting China and building ties with Japan.
Although South Korea exchanged military intelligence and found it unavoidable to expand security cooperation with Japan to deal better with North Korea, he said no trilateral military exercises with the United States and Japan were on the horizon.
During his campaign, he indicated that he would push for the deployment of a second Thaad battery in South Korea, but he told The Times that his country would review its usefulness before taking further steps.
Perhaps most revealing, Mr. Yoon did not meet Speaker Nancy Pelosi when she came to Seoul after her high-stakes visit to Taiwan last month. His decision led to speculation that he was trying to avoid offending China, which claims Taiwan as its own and firmly opposed Ms. Pelosi’s visit.
Mr. Yoon called those suggestions “absolutely” untrue and said he was simply on a scheduled vacation. On Friday, though, Mr. Yoon met with Li Zhanshu, the head of the Chinese legislature and the third-highest-ranking member of the Chinese Communist Party.
“I seek to find the answer in strengthening the extended deterrence based on a strong South Korea-U.S. alliance,” he said. “Extended deterrence includes not only the use of nuclear weapons based in American territory, but also a package of all possible means and methods to deter nuclear provocations by North Korea.”
Yet like all his predecessors, he left the door open for dialogue. If North Korea moved toward denuclearization, he said, South Korea would start providing economic assistance, even before the denuclearization was complete.
The North’s response to what Mr. Yoon has described as an “audacious initiative” has been anything but encouraging. Last month, the North called the South Korean president “simple” and “childish.” Mr. Cheong, the analyst, called Mr. Yoon’s proposal a revamped version of previous governments’ failed approach.
But Mr. Yoon, whose government has been dogged by one domestic scandal after another, seemed hopeful that North Korea would come around to seeing things his way. “If they care about their people and make a rational decision,” he said, “they will start reducing their nuclear stockpile.”