North Korea's ruling party is getting ready to meet

A U.S. U-2S reconnaissance aircraft lands at Osan Air Base in Pyeongtaek, Gyeonggi amid heightened speculation that North Korea could conduct a seventh nuclear test in the coming days. [YONHAP]

North Korea's Workers' Party Politburo gathered on Tuesday to set an agenda for a party meeting to take place soon, state media said Wednesday.

The gathering of the top tier of the North's ruling party came as speculation mounts that the regime has completed preparation for a possible seventh nuclear weapons test.

Jo Yong-won, secretary for organizational affairs of the ruling Workers' Party's Central Committee, presided over the Politburo meeting on Tuesday, according to the state-run Korean Central News Agency (KCNA).

North Korean leader Kim Jong-un did not attend.

The Politburo meeting precedes a plenary session of the Central Committee of the ruling party that the KCNA said will take place in early June to decide on a "series of important issues."

The announcement of the plenary session came amid widespread fears of a seventh nuclear test.

The director-general of the International Atomic Energy Agency (IAEA), Rafael Grossi, told the agency's Board of Governors on Monday in Vienna that one of the tunnel entrances at the Punggye-ri nuclear test site, located in North Korea's remote mountainous North Hamgyong Province, has been reopened ahead of a potential nuclear test.

All of the North's six previous tests took place underground at Punggye-ri.

The nuclear watchdog chief's report follows satellite imagery analysis and assessments by South Korean and U.S. intelligence officials in recent months that have concluded the North is nearing the end of preparations to conduct a test.

These steps included excavating tunnels and constructing buildings, most of which were demolished in May 2018 when Pyongyang declared a self-imposed moratorium on major weapons tests.

The upcoming plenary session of the Workers' Party may also provide clues about the regime's foreign and military policies, now that Seoul and Washington have vowed heightened cooperation following U.S. President Joe Biden and South Korean President Yoon Suk-yeol's summit in Seoul on May 21.

In a move sure to anger Pyongyang, Biden and Yoon agreed to revive the U.S.-Korea Extended Deterrence Strategy and Consultation Group (EDSCG), deploy additional U.S. strategic assets to the Korean Peninsula, and expand joint military exercises between South Korea and the U.S.

The South Korean and U.S. militaries have since staged a series of joint exercises.

The allies' militaries flew 20 fighter jets over the Yellow Sea to the west of the peninsula on Tuesday in a show of force that Seoul's Joint Chiefs of Staff (JCS) said involved 16 South Korean planes — including F-35A stealth fighters — and four U.S. F-16 fighter jets and demonstrated the allies' ability to respond swiftly to aggression by the North.

The joint air exercise came after the allies fired eight surface-to-surface MGM-140 Army Tactical Missile System (Atacms) missiles on Monday morning in a tit-for-tat response to North Korea launching eight short-range ballistic missiles (SRBM) into waters east of the Korean Peninsula on Sunday.

South Korea and the United States also recently wrapped up joint naval drills involving the aircraft carrier USS Ronald Reagan off the Japanese island of Okinawa over the weekend. The exercises were the allies' first to involve a U.S. aircraft carrier since 2017.

The USS Reagan is now involved in one of the U.S. Indo-Pacific Command's largest military exercises, Valiant Shield, which began on Monday.

Valiant Shield prepares U.S. troops to respond to hot spots in East Asia and beyond, ranging from North Korea to the East China Sea, the South China Sea and Taiwan.

Two carrier strike groups, led by the aircraft carriers USS Ronald Reagan and USS Abraham Lincoln, are participating in the exercise, as are the USS Tripoli amphibious assault ship, two Marine expeditionary forces, the U.S. Air Force's 36th Wing, 15 surface ships, more than 200 aircraft and an estimated 13,000 personnel, according to a statement by Indo-Pacific Command.

BY MICHAEL LEE [lee.junhyuk@joongang.co.kr]