Ruling party presidential candidate Lee Jae-myung has said South Korea should maintain good relations with its largest trading partner China despite Beijing's "increasingly assertive behavior," saying China's cooperation is key to addressing various issues in the region and beyond, including North Korea.

Lee of the liberal Democratic Party made the comment in an article he contributed to Foreign Affairs magazine, titled "A Practical Vision for South Korea," outlining his views on the way forward in South Korea's relations with the United States, North Korea and Japan.

"South Korea must ... maintain a partnership with China, which is the country's largest trading partner, accounting for a quarter of South Korea's trade volume," Lee wrote.

"Pragmatism dictates that in order to address critical issues such as North Korea's nuclear program, peace and stability on the Korean Peninsula, cross-border environmental pollution, and the COVID-19 response, Seoul needs to get along with Beijing," he said.

Lee went further to add, "This is not to say South Korea should be accommodating to China, and South Koreans have good reason to be concerned by Beijing's increasingly assertive behavior.

"But overt antagonism serves neither South Korea's national interests nor its alliance with Washington," he continued. "Without Beijing's cooperation in persuading North Korea to abandon its nuclear program, North Korea will depend more on China, making it more difficult to find a resolution to Pyongyang's nuclear and missile programs."

Lee rejected criticism that South Korea has maintained "strategic ambiguity" between the United States and China in what has effectively been seen as a "tilting away" from its ally, the US.

"This claim is simply wrong," he said. "There is nothing ambiguous about South Korea's stance. The United States is the sole treaty ally of the Republic of Korea. The alliance was forged in the fire of the Korean War and over time has evolved into a comprehensive partnership."

Lee acknowledged that the "thorniest problem" facing South Korea is North Korea's nuclear and missile programs.

He said Seoul will continue to make North Korean leader Kim Jong-un understand that South Korea, through its alliance with the US, "is absolutely resolute and capable of dealing firmly with any military strikes or provocations."

But he stressed any solution for North Korea's denuclearization must be peaceful.

"Saber rattling achieves little: glibly advocating for a preemptive strike against Pyongyang, for example, evokes Cold War posturing that is no longer relevant and serves only to stoke fear and division," he said, alluding to the words of his rival and main opposition candidate Yoon Suk-yeol of the conservative People Power Party.

"A second Korean War, which would likely be a nuclear war, is unacceptable," he continued.

"It is important to win a war; it is even more important to win without a war. This can be achieved with a mixture of deterrence, diplomacy, and dialogue," he said, crediting the US Joe Biden administration for emphasizing this approach through its "calibrated and practical" approach to North Korea.

Lee outlined his vision for implementing a denuclearization deal with North Korea in phases. He also called for providing humanitarian assistance to the North to support the effort.

On relations with Japan, Lee expressed regret over "Tokyo's unwillingness to let go of its imperial past," which he said "continues to hamper trilateral cooperation between Japan, South Korea, and the United States."

He also described Japan's 2019 export controls against South Korea as "a shocking act of economic coercion to settle a historical grudge."

Lee said the two countries should look back to the spirit of a 1998 joint declaration between then South Korean President Kim Dae-jung and then Japanese Prime Minister Keizo Obuchi, in which Japan "unprecedentedly expressed remorse and offered a heartfelt apology" for its 1910-45 colonial rule of the Korean Peninsula. (Yonhap)