In NATO’s most serious denunciation of China to date, the military coalition labeled Beijing a “decisive enabler” of Russia in its ongoing war in Ukraine and expressed concerns over its nuclear arsenal and “systemic challenges” to the coalition’s security.

“The PRC has become a decisive enabler of Russia’s war against Ukraine through its so-called ‘no limits’ partnership and its large-scale support for Russia’s defence industrial base,” a NATO communique said Wednesday, on the second day of a Washington summit celebrating the alliance’s 75^th anniversary.  

The coalition further called on Beijing to “cease all material and political support to Russia’s war effort,” specifically naming the transfer of “dual-use materials, such as weapons components, equipment, and raw materials that serve as inputs for Russia’s defence sector” — in NATO’s first explicit accusation that the administration of Xi Jinping is providing military aid to Moscow.

“It’s the first time that NATO allies state this so clearly in an agreed document,” NATO Secretary-General Jens Stoltenberg said in a Wednesday address. “It cannot continue like this without it impacting the interests and reputation of China.”

NATO has been deeply entrenched in its support for non-member Ukraine since the dawns of Russia’s invasion, widely viewing Moscow as a potential threat to broader European security.

Beijing has previously repeatedly denied supplying weapons to Russia in the war in Ukraine, but the two nations have maintained close trade relations throughout the conflict, even as Moscow finds itself increasingly divorced from or outright sanctioned by the West. A CNBC analysis last year found that Moscow was at the time sourcing semiconductors and other advanced Western technologies through intermediary countries, including China.

Earlier this week, Beijing started joint military exercises with Russia’s close ally Belarus at a training ground mere miles away from the Polish border, the Belarusian Defense Ministry said in a Google-translated Telegram post. The territory of Belarus previously served as a launching pad for Russia’s invasion of neighboring Ukraine.

On the February 2023 first-year anniversary of the Ukraine war, China — which a month later successfully capitalized on goodwill earned as a trade partner to broker a reconciliation between arch-enemies Iran and Saudi Arabia — pitched a peace framework for the conflict between Moscow and Kyiv. It, like Ukrainian President Volodymyr Zelenskyy’s peace plan and Kremlin leader Vladimir Putin’s own recent conditions to ignite diplomatic negotiations, has so far failed to gain traction.

Earlier this week, China was the third stop in the world tour of Hungarian Prime Minister Viktor Orban, a crucial Putin ally who debuted his self-declared “peace mission” to resolve the conflict in Ukraine. After visiting Ukraine and Russia, Orban met with Xi in Beijing, praising China as a “key power” to resolve the hostilities.

After years of a velvet-gloved diplomacy and approaching China as a distant concern, NATO on Wednesday said Beijing “continues to pose systemic challenges to Euro-Atlantic security,” underscoring the alleged disinformation stemming from the world’s second-largest economy and its activities in space and cyberspace.

Back in March, NATO members the U.S. and U.K. accused China of a years-long cyberespionage campaign against politicians, businesses and journalists. The practices exposed “China’s continuous and brash efforts to undermine our nation’s cybersecurity and target Americans and our innovation,” FBI Director Christopher Wray said at the time.

In response, the Chinese embassy to the U.K. condemned Britain’s “sinister action.” “The UK’s claim that China was responsible for malicious cyber campaigns targeting the U.K. is completely unfounded and constitutes malicious slander,” it said at the time.

NATO also raised alarms over China’s alleged nuclear ambitions.

“The PRC continues to rapidly expand and diversify its nuclear arsenal with more warheads and a larger number of sophisticated delivery systems. We urge the PRC to engage in strategic risk reduction discussions and promote stability through transparency,” the NATO communique said, warning that allies are simultaneously raising their “shared awareness” and enhancing preparations to protect against China’s “coercive tactics and efforts to divide the Alliance.”

The Federation of American Scientists estimates that China has a total inventory of 500 warheads as of March — a mere 9% of the arsenal of Russia, which possesses the largest nuclear capabilities after inheriting the reserves of the former Soviet Union.

“China is expanding its nuclear arsenal faster than any other country,” Hans Kristensen, associate senior fellow at the Stockholm International Peach Research Institute said back in June, when the institute released its yearly publication analyzing world nuclear powers.

“The Chinese nuclear stockpile is projected to continue growing over the coming decade and the number of Chinese intercontinental ballistic missiles (ICBMs) is likely to reach or even exceed the numbers held by either the Russian Federation or the United States,” SPRI found last month.

CNBC has reached out to China’s Ministry of Foreign Affairs. In a scathing riposte, China’s mission to the European Union said that the NATO statement “hypes up China-Russia relations undercutting and reshaping the rules-based international order” and is “filled with Cold War mentality and belligerent rhetoric.”

It added, “The China-related paragraphs are provocative with obvious lies and smears. We firmly reject and deplore these accusations and have lodged serious representations with NATO.”

The NATO comments to China come after the leaders of several Indo-Pacific countries — such as Australia, Japan, New Zealand and South Korea — are attending the Washington NATO summit, according to Reuters, extending a practice that began after Russia’s invasion of Ukraine.