South Korea's president-elect Yoon Suk-yeol speaks during a news conference at the National Assembly in Seoul, South Korea, March 10, 2022.
South Korea's president-elect Yoon Suk-yeol speaks during a news conference at the National Assembly in Seoul, South Korea, March 10, 2022. Reuters / KIM HONG-JI

South Korea's president-elect Yoon Suk-yeol said on Thursday strong deterrence was crucial in the face of nuclear and missile threats from North Korea amid a renewed warning by a top U.S. envoy of a potential nuclear test as early as next week.

Yoon, who has pledged to boost defence capability to counter the North's threats, spoke to U.S. Forces Korea (USFK) Commander Gen. Paul LaCamera during a rare visit to Camp Humphreys in Pyeongtaek, the command centre of the 28,500-strong U.S. military stationed in South Korea.

"We can never stress enough the importance of strong deterrence based on the South Korea-U.S. military alliance and the combined defence posture," Yoon said, citing the alarm raised by the North's test launch of an intercontinental ballistic missile (ICBM) last month.

Officials in Seoul and Washington have indicated Pyongyang may resume testing nuclear weapons for the first time since 2017, possibly around the birth annivesary of state founder Kim Il Sung, which the North celebrates on April 15.

"I don't want to speculate too much, but I think it could be another missile launch, it could be a nuclear test," Sung Kim, the U.S. special representative for North Korea, told reporters on a teleconference on Wednesday in Washington when asked about the holiday next week.

Signs of preparations for a nuclear test included activity near the North's Punggye-ri nuclear site, U.S. officials said.

North Korea launched a new ICBM last month after leader Kim Jong Un threatened to break his self-imposed moratorium on ICBM and nuclear testing.

Kim's powerful sister, Kim Yo Jong, has warned Pyongyang could use nuclear weapons if the South attacked, with South Korea and the United States expected to stage regular springtime exercises that Pyongyang has long denounced as a war rehearsal.

Yoon's visit to Camp Humphreys, the largest U.S. overseas military base, also comes as his foreign policy and security aides discussed possible redeployment of U.S. strategic assets to the peninsula with U.S. officials in Washington.

Yoon is set to be sworn in on May 10.