US Secretary of Defense Lloyd Austin (left) shakes hands with South Korean Defense Minister Lee Jong-sup after a joint press conference after their meeting at the Defense Ministry in Seoul, South Korea, on Jan 31, 2023. (PHOTO / AP)

SEOUL - The defense chiefs of the United States and South Korea vowed on Tuesday to expand military drills and boost nuclear deterrence.

US Defense Secretary Lloyd Austin was in Seoul for talks as Washington seeks to reassure a key Asian ally over its nuclear commitment.

Austin met with South Korean Defense Minister Lee Jong-sup, following their annual security talks in November in Washington, and was due to meet with President Yoon Suk-yeol before flying to the Philippines.

The latest meeting comes as South Korea pushes to bolster confidence in American extended deterrence - its military capability, especially nuclear forces.

US Defense Secretary Lloyd Austin said his trip was aimed at deepening cooperation to tackle shared security challenges and reaffirm the US extended deterrence commitment to South Korea as "ironclad"

In a joint statement, the defense chiefs said they had agreed to boost information sharing and joint planning.

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They also committed to expand the "level and scale" of this year's combined military exercises, and to deploy more US strategic assets, such as aircraft carriers and bombers.

Austin said his trip was aimed at deepening cooperation to tackle shared security challenges and reaffirm the US extended deterrence commitment to South Korea as "ironclad".

"That's why the United States and the ROK are taking clear, meaningful steps to modernize and strengthen our alliance," Austin said in a special op-ed release on Tuesday by Yonhap news agency, referring to South Korea by the initials of its official name, the Republic of Korea.

US Secretary of Defense Lloyd Austin and his South Korean counterpart Lee Jong-sup attend a welcome ceremony at the Defense Ministry in Seoul, South Korea, on Jan 31, 2023. (PHOTO / AP)

"So our adversaries and competitors know that if they challenge one of us, they are challenging the US-ROK alliance as a whole," he added.

Lee has said the two countries will hold nuclear tabletop exercises in February, as part of efforts to improve joint nuclear planning and implementation and boost information sharing.

READ MORE: South Korea, US plan February nuclear tabletop drills

Austin said the exercises are in line with the allies' talks to expand extended deterrence activities.