"It's an anachronistic idea that North Korea will use nuclear weapons for the unification (of the two Koreas)," he said, responding to a question after a keynote speech at the Fullerton Forum hosted by the International Institute for Strategic Studies.

Song also defended the Moon Jae-in administration's efforts for dialogue with the North.

"It may be a rough path, which could take a long time. But I think we have to go that way by being patient and patient again," he added.

On the weekend, the minister had bilateral talks with the US Secretary of Defense Jim Mattis in Hawaii, where the two defense chiefs reaffirmed the ironclad alliance between the two countries in the face of the North's recent peace offensive.

They emphasized that "any efforts to drive a wedge in the US-ROK (South Korea) alliance would fail," as they stick to the shared goal of denuclearizing the North in a "complete, verifiable and irreversible" manner, according to a press release. (Yonhap)