White House Press Secretary Karine Jean-Pierre is seen answering questions during a daily press briefing at the White House in Washington, Jan. 3. Yonhap

The United States remains fully committed to defending South Korea against any hostility, including a nuclear attack by North Korea, White House Press Secretary Karine Jean-Pierre said Tuesday.

She said the allies are also working to further improve their joint readiness.

"The United States is fully committed to our alliance with the ROK, providing extended deterrence through the full range of U.S. defense capabilities," the spokesperson told a daily press briefing, referring to South Korea by its official name, the Republic of Korea.

Her remarks come after President Joe Biden said "no" when asked if the U.S. was discussing holding joint nuclear exercises with South Korea.

A South Korean newspaper earlier reported South Korean President Yoon Suk-yeol as saying that the countries are discussing such drills.

Jean-Pierre noted joint nuclear exercises are held between nuclear states, as explained earlier by Yoon's presidential office, while underlining the fact that Yoon and Biden have instead instructed their governments to further enhance their joint defense readiness based on U.S. extended deterrence.

"Following their meeting in Cambodia, President Biden and President Yoon tasked their teams to plan for an effective, coordinated response to a range of scenarios, including nuclear use by North Korea, and so that is what the teams are working on, and what President Yoon was clearly referencing when he made his comments," she told the press briefing.

North Korean leader Kim Jong-un, center, attends a ceremony of donating 600mm super-large multiple launch rocket system at a garden of the Workers' Party of Korea headquarters in Pyongyang, North Korea, in this Dec. 31, 2022 file photo. AP-Yonhap

State Department spokesperson Ned Price underscored U.S. commitment to providing extended deterrence to South Korea.

"In terms of extended deterrence, we are fully committed to our alliance with the ROK and providing extended deterrence through the full range of U.S. defense capabilities," he told a department press briefing.

"We are continuing to have discussions to see to it that extended deterrence is meaningful and that we can demonstrate both in word and in deed that our commitment to the security of the ROK and Japan as our treaty allies is ironclad," he added.

North Korea has openly threatened to preemptively use its tactical nuclear weapons against South Korea.

Also in a recently concluded plenary meeting of the ruling Workers' Party, North Korean leader Kim Jong-un called on his country to "exponentially" expand its nuclear arsenal while labeling South Korea an "undoubted enemy."

Price said it was "unfortunate" that North Korea appears to have embraced provocation over dialogue.

"We have made repeatedly clear that we harbor no hostile intent towards the DPRK. We are prepared to engage in constructive, good-faith principle dialogue towards what is our ultimate goal. That is the complete denuclearization of the Korean Peninsula," he added.

DPRK stands for the Democratic People's Republic of Korea, the North's official name. (Yonhap)