As Yoon Suk-yeol takes office as South Korean president on Tuesday, he will be greeted with North Korea’s rapidly expanding nuclear arsenal as leader Kim Jong Un seeks to make up for Pyongyang’s military weaknesses against Washington and its Asian allies.

Amid stalled denuclearization talks with the United States, Kim vowed in late April to bolster his country’s nuclear arsenal in both “quality and scale,” and expand it “at the fastest possible speed.” The warning, issued during a nighttime military parade, came as Pyongyang seems to be taking a more aggressive nuclear posture that could potentially include pre-emptive nuclear strikes.

The growing tensions with North Korea are expected to top the agenda when Yoon meets U.S. President Joe Biden on May 21. Yoon, who is seeking to strengthen his country’s military alliance with Washington, has asked the U.S. to redeploy strategic assets to South Korea, as Pyongyang continues to advance its nuclear weapon and missile programs, despite U.N. Security Council sanctions and high-level diplomatic efforts. Biden will also visit Tokyo on his first trip to the region as president.