South Korea and the U.S. have engaged in talks to involve Seoul in U.S. nuclear weapons management amid increasingly hostile tensions with neighboring North Korea.

South Korean President Yoon Suk Yeol told reporters Monday that South Korea was pushing for joint planning and training involving U.S. nuclear assets, an idea the U.S. responded positively to, according to an Associated Press report Tuesday.

However, President Biden denied that such talks were taking places when asked by reporters later Monday if there were any discussions about joint nuclear exercises, flatly responding, "no."

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Kamala Harris greeting President Yoon

Vice President Kamala Harris shakes hands with South Korea's President Yoon Suk-Yeol. (LEAH MILLIS/POOL/AFP via Getty Images)

Biden's response to the question appeared to catch the South Koreans off guard, with Yoon’s top adviser for press affairs, Kim Eun-hye, issuing a statement later Tuesday reiterating that the two sides "are discussing an intel-sharing, a joint planning and subsequent joint execution plans over the management of U.S. nuclear assets in response to North Korea's nuclear (threats)."

Kim also speculated that Biden replied "no" to the question because it was poorly asked by the reporter, and the president was not provided any background information.

The news comes amid heightened tensions on the Korean Peninsula, with North Korea launching a record number of weapons tests and escalating its rhetoric toward both Japan and South Korea.

The isolated country's threatening posture has seemingly increased U.S. and South Korean military cooperation, with the two sides unveiling last month that the South Korean and U.S. militaries are planning over 20 joint drills this year in response to the threats from North Korea.

Joe Biden makes speech

President Joe Biden. (Reuters)

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However, cooperation in nuclear weapons management would be a dramatic shift.

South Korea does not possess any nuclear weapons and is instead part of the U.S. "nuclear umbrella," an agreement that promises a devastating American response to an attack on a U.S. ally. 

Yoon said that the new arrangement would keep nuclear weapons in the hands of the U.S. military, but intel-sharing and exercises involving the weapons would be jointly conducted with South Korea.

Shirtless South Korean Marines and their U.S. counterparts from 3-Marine Expeditionary Force 1st Battalion from Kaneho Bay, Hawaii, run on a snow covered field during their Feb. 4-22 joint military winter exercise in Pyeongchang, east of Seoul, South Korea, Thursday, Feb. 7, 2013. More than 400 marines from the two countries participated in the joint winter exercise held for the first time in South Koreas. (AP Photo/Lee Jin-man)

Shirtless South Korean Marines and their U.S. counterparts from 3-Marine Expeditionary Force 1st Battalion from Kaneho Bay, Hawaii, run on a snow covered field during their Feb. 4-22 joint military winter exercise in Pyeongchang, South Korea. (AP2013)

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Reached for comment by Fox News Tuesday, a White House National Security Council spokesperson stressed that the cooperation between the two countries did not amount to joint nuclear exercises.

"As the President said, we are not discussing joint nuclear exercises," the spokesperson said. "The ROK is a non-nuclear weapons state. The United States is fully committed to our alliance with the ROK and providing extended deterrence through the full range of U.S. defense capabilities. Following their meeting in Phnom Penh, 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. That is what the teams are working on."

The Associated Press contributed to this report.