Washington and Seoul will conduct "increasingly complex scenario-based tabletop exercises focused on nuclear threats on the peninsula," Austin wrote in an op-ed published by the Yonhap news agency, without specifying when this would occur.

Austin is visiting Seoul for the third time as defence secretary, during which he is to meet with his South Korean counterpart Lee Jong-sup and President Yoon Suk-yeol.

His visit is aimed at deepening cooperation and discussing security challenges, as well as reaffirming "that the US extended deterrence commitment to the ROK (Republic of Korea) is ironclad," he wrote.

Military tensions on the Korean peninsula rose sharply last year as the North conducted sanctions-busting weapons tests nearly every month, including firing its most advanced intercontinental ballistic missile.

North Korean leader Kim Jong Un also recently called for an "exponential" increase in Pyongyang's nuclear arsenal, and declared the North an "irreversible" nuclear state last year.