Seoul (AFP) - US Defense Secretary Lloyd Austin and his South Korean counterpart held talks in Seoul on Tuesday, pledging to step up military exercises and security cooperation as Seoul seeks reassurances in the face of North Korea's nuclear threats.

Seoul is keen to persuade a public increasingly wary of US "deterrence" commitments, a year after North Korea declared its nuclear power status "irreversible" and conducted banned weapons tests almost every month.

Austin and Lee Jong-sup agreed to "expand and enhance the level and scale" of the joint military exercises, in light of "increasing provocations" from Pyongyang, including recent drone incursions, they said in a statement.

Military tensions on the Korean Peninsula escalated sharply in 2022, with North Korea conducting a record number of weapons tests, including the launch of its most advanced intercontinental ballistic missile.

Pyongyang sent five marches across the border on December 26, the first such incident in five years, prompting Seoul to send warplanes.

Austin and Lee agreed to "expand and enhance the level and volume of joint exercises and exercises further this year," Lee said at a press briefing in Seoul.

This was deemed necessary given "changes in the security environment, including North Korea's attempts to upgrade its nuclear and missile programmes."

The two security allies will hold "theoretical exercises" in February to improve communication on "deterrence and response options" to Pyongyang's nuclear threats.

"We're going to do a number of theoretical exercises to check for consensus," Austin said at the press briefing.

Any joint US-South Korean military exercises would anger Pyongyang, which it considers a prelude to an invasion and has often responded with threats or drills for its forces.

Visiting Seoul for the third time since taking over as defense minister, Austin met with Lee and South Korean President Yoon Sok-yul.

This month, Yoon touched on the idea of acquiring nuclear weapons. It is the first time in decades that a South Korean president has put forth such an idea, reflecting growing domestic concern about the reliability of US security commitments.

However, the Yoon administration retracted those statements, stressing that South Korea supports global nuclear non-proliferation.

Austin reaffirmed Tuesday the US commitment to strengthening deterrence, saying that US military assets, especially nuclear forces, deter attacks on allies.

He said the commitments cover "all areas of US defense capabilities, including our conventional nuclear defense capabilities and missile defense."

The North Korean leader recently called for a "massive" increase in Pyongyang's nuclear arsenal, including mass production of tactical nuclear weapons and the development of new missiles for use in nuclear counter-strike.

Kim said his country should "largely build up military power" in 2023 in response to what he described as US and South Korean hostility.

Hong Min, of the Korea Institute for National Unification, told AFP that Austin's visit aims to "assuage growing concerns among South Korean citizens and politicians about whether the United States can be trusted to bolster deterrence against North Korean nuclear threats."

"With agreement on a detailed set of US assets to be deployed in joint exercises, Washington seems keen to dispel those concerns," he said.