BEIJING (Kyodo) -- North Korean leader Kim Jong Un has called for the bolstering of the country's nuclear forces this year during a tour of a nuclear-material production base and the Nuclear Weapons Institute, state-run media said Wednesday, publishing pictures of many centrifuges at a facility.

In an apparent reference to the United States and South Korea, Kim said his country faces "the world's most unstable situation in which a long-term confrontation with the most vicious hostile countries is inevitable," the official Korean Central News Agency said.

Such a situation "makes it indispensable for the country to steadily strengthen the nuclear shield," Kim was quoted as saying. He added 2025 is "a crucial year" and "an important watershed in which we should carry out the tasks in the important period in the course of implementing the line of bolstering up the nuclear forces."

KCNA did not disclose the location of the site or when Kim was there. The leader last visited a similar production base of weapons-grade nuclear materials last September.

Kim also said that "the absolute force capable of thoroughly containing the enemies and taking the initiative to control the situation is not provided by any declaration or slogan, but the stockpiling of the physical strength of practical use and its increase by geometrical progression," according to the report.

During the visit to the nuclear facility, Kim was accompanied by Hong Sung Mu, first deputy department director of the Central Committee of the ruling Workers' Party of Korea, who is believed to be a central figure in the country's nuclear weapons development.

In 2010, Pyongyang gave U.S. nuclear expert Siegfried Hecker a tour of a uranium enrichment facility in Yongbyon in the country's northwest.

North Korea, which has conducted six nuclear tests since 2006, is believed to be able to produce plutonium and highly enriched uranium for nuclear weapons at the Yongbyon complex. The country also has a similar facility in Kangson near Pyongyang.

At their summit in Hanoi in 2019, Kim and U.S. President Donald Trump fell short of a deal, with Washington insisting that North Korea denuclearize and Pyongyang demanding economic sanctions relief.

Trump said Kim pledged to "totally" dismantle the Yongbyon nuclear complex used to produce weapons fuel, but the lifting of the sanctions would require Pyongyang to scrap other nuclear facilities and programs, including undeclared ones.

Since returning to the White House on Jan. 20, Trump has said he intends to reengage with Kim, with whom he held in-person meetings three times during his first presidency, including the Vietnam talks.