Pyongyang, North Korea - North Korea vowed Saturday to advance its nuclear capabilities, reacting to a report that the US had revised its own nuclear strategic plan.

The country will "bolster up its strategic strength in every way to control and eliminate all sorts of security challenges that may result from Washington's revised plan," the official Korean Central News Agency (KCNA) reported.

The New York Times reported this week that a US plan approved by President Joe Biden in March was to prepare for possible coordinated nuclear confrontations with Russia, China, and North Korea.

The highly classified plan for the first time reorients Washington's deterrent strategy to focus on China's rapid expansion in its nuclear arsenal, the Times said.

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KCNA said North Korea's foreign ministry "expresses serious concern over and bitterly denounces and rejects the behavior of the US."

It added North Korea vowed to push forward the building of nuclear force sufficient and reliable enough to firmly defend its sovereignty.

Pyongyang and Moscow have been allies since North Korea's founding after World War II and have drawn even closer since Russia's 2022 invasion of Ukraine.

The US and Seoul have accused North Korea of providing ammunition and missiles to Russia for its war in Ukraine.

Pyongyang, which has declared itself an "irreversible" nuclear weapons power, has described allegations of supplying weapons to Russia as "absurd."

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However, it did thank Russia for using its United Nations veto in March to effectively end monitoring of sanctions violations just as UN experts were starting to probe alleged arms transfers.

China presents itself as a neutral party in Russia's offensive on Ukraine and says it is not sending lethal assistance to either side, unlike the US and other Western nations.

But it is a close political and economic ally of Russia, and NATO members have sought to brand Beijing a "decisive enabler" of the war.

Moscow has looked to Beijing as an economic lifeline since the Ukraine conflict began, with the two boosting trade to record highs as Russia faces heavy sanctions from the West.

The US has also boosted military drills and arms sales to South Korea and Japan, including a recent deal to send Apache helicopters to Seoul which Pyongyang has blasted as a "reckless, provocative act."