South Korea and the United States are discussing joint planning and implementation of operations involving U.S. nuclear assets to counter North Korea’s threats, Seoul’s presidential office said on Tuesday.

The statement came shortly after U.S. President Joe Biden said the United States was not discussing joint nuclear exercises with South Korea, contradicting earlier remarks by South Korean President Yoon Suk-yeol in an interview with a local newspaper.

“In order to respond to the North Korean nuclear weapons, the two countries are discussing joint ways to share information on the operation of .U.S-owned nuclear assets, and joint planning and joint execution of them accordingly,” Yoon’s press secretary, Kim Eun-hye, said in a statement.

Kim said President Biden “had no choice but to say ‘No'” because he was simply asked if the two countries were “discussing nuclear war games,” whereas joint nuclear exercises can only be held between nuclear weapons states.