North Korea broke its silence on President Park Geun-hye’s visit to China a day after the South Korean leader returned home after forging deeper personal bonds with her Chinese counterpart and agreeing to bolster cooperation between the two countries.

In a statement issued Monday by the Committee for the Peaceful Reunification of the Fatherland, an organization in charge of cross-border affairs, Pyongyang lambasted Park for her demand that it should abandon its nuclear weapons programs.

“Our nuclear capability can never become a bargaining tool and is not negotiable,” the statement said. It further criticized Park for having defamed the North’s dignity and regime through her remarks and acts during her visit to China.

It may not be difficult to guess how the North Korean leadership felt at the sight of Park and Chinese President Xi Jinping spending a combined 7 1/2 hours together over two days, from Thursday’s summit to Friday’s special lunch Xi hosted in an unusual show of hospitality.

It was certainly far from consoling to Pyongyang that a joint statement released after their summit stopped short of clearly stating that a nuclear North Korea was unacceptable. Park and Xi made it clear that Pyongyang’s nuclear program posed a serious threat to regional and world peace, and pledged to work closely together to make the Korean Peninsula free of atomic weapons.

Xi also endorsed Park’s approach to inter-Korean relations, saying he was optimistic about her trust-building process with the North. U.S. President Barack Obama also backed the initiative during his summit with Park in May. With the support from the leaders of the two superpowers, Park is now in a position to push for her signature policy on the North, which calls for stern responses to provocations, while leaving the door for dialogue open.

North Korea now sees that its move to heighten tensions with nuclear threats and bellicose rhetoric over the past months has only made it even more isolated and brought mounting pressure on itself to discard its nuclear weapons. Before it is too late, Pyongyang should realize that the only way to guarantee its survival will be to give up its nuclear programs and sit down with neighboring powers for sincere talks.

Seoul may need to work out a more sophisticated and strategic plan to induce the North to change course.