'Irreversible nuclear state': North Korea builds secret military base; absent from US–Pyongyang nuclear talks

North Korea has secretly constructed a missile base near its border with China that could be home to some of its most advanced long-range nuclear weapons, according to new research released Wednesday.

The "undeclared" Sinpung-dong Missile Operating Base is located about 27 kilometres (17 miles) from the Chinese frontier, the Washington-based Center for Strategic and International Studies (CSIS) said in a report published Wednesday.

The facility in North Pyongan Province likely houses six to nine nuclear-capable intercontinental ballistic missiles (ICBMs) and their launchers, the study said. It added that the weapons "pose a potential nuclear threat to East Asia and the continental United States".

CSIS described its report as the first in-depth, open-source confirmation of Sinpung-dong. It said the base is one of about "15-20 ballistic missile bases, maintenance, support, missile storage, and warhead storage facilities which North Korea has never declared". The facility is "not known to have been the subject of any denuclearisation negotiations previously conducted between the United States and North Korea", the study said.

According to CSIS, the launchers and missiles could leave the base in times of crisis or war, link up with special units and conduct harder-to-detect launches from other parts of the country. The base, along with others, "represent the primary components of what is presumed to be North Korea's evolving ballistic missile strategy, and its expanding strategic-level nuclear deterrence and strike capabilities".

North Korea has expanded its nuclear weapons programme since the collapse of a summit with the United States in 2019. Kim’s meeting with US President Donald Trump in Hanoi fell apart because the two sides disagreed on what Pyongyang would concede in return for sanctions relief.

Since then, Kim Jong Un has called for the "rapid expansion" of the nation's nuclear capability and declared North Korea an "irreversible" nuclear state.

Russia–North Korea ties raise new concerns

In the wake of Russia’s invasion of Ukraine, Pyongyang has drawn closer to Moscow. South Korean and Western intelligence agencies say the North sent more than 10,000 soldiers to Russia in 2024 — primarily to the Kursk region — along with artillery shells, missiles and long-range rocket systems.

Washington has said there is evidence that Russia is stepping up support for North Korea, including help on advanced space and satellite technology, in return for its assistance in the war. Analysts note that satellite launchers and ICBMs share much of the same underlying technology.