NATO leaders on Wednesday accused China of being a "decisive enabler" of Russia's ongoing war against Ukraine, in their harshest criticism yet of the Asian power that is seen by the transatlantic military alliance as continuing to pose challenges to the rules-based international order.

A joint declaration, endorsed by the leaders of the 32-member North Atlantic Treaty Organization during a summit in Washington, also said they "strongly condemn" North Korea's exports of artillery shells and ballistic missiles for use in the war in Ukraine.

"The deepening strategic partnership between Russia and (China) and their mutually reinforcing attempts to undercut and reshape the rules-based international order, are a cause for profound concern," they said.

Using much stronger language about China than in past NATO statements, the leaders urged Beijing to cease all material and political assistance for Russia's war effort.

NATO Secretary General Jens Stoltenberg said at a press conference that it is the first time that all members of the alliance, accounting for 50 percent of the global economy, have declared concerns over China to this extent.

While China, trying to portray itself as a neutral actor in the war, has denied providing direct military aid to Russia, Western officials have raised alarm over their closer alignment in recent months.

They believe China's transfer of dual-use materials, including microelectronics and nitrocellulose, to Russia is revitalizing its military-industrial base.

Stoltenberg said NATO is not an organization that can impose economic sanctions, unlike the European Union, but underscored that the alliance's message is clear, warning that China's interests will be impacted if it continues to support Russia's military industry.

The declaration, released on the second day of the three-day summit, stated that China has a particular responsibility to uphold the principles of the U.N. Charter, given that it is a permanent member of the world body's Security Council.

Reiterating that China continues to pose "systematic challenges" to Euro-Atlantic security, the leaders expressed concerns over Beijing's actions in other areas as well, including the rapid development of its nuclear arsenal and "malicious" cyber activities.

China quickly lashed back at the NATO communique, slamming it as being "filled with Cold War mentality and belligerent rhetoric."

"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 Chinese Mission to the European Union said in a statement.

On Ukraine, NATO announced a new set of measures aimed at shoring up near- and long-term support for the war-torn country.

They included providing at least 40 billion euros ($43 billion) in support of Ukraine next year and stationing a civilian as NATO's senior representative in Kyiv to help facilitate communications between the alliance and Ukrainian authorities.

The leaders said "Ukraine's future is in NATO," welcoming that the country's armed forces have become more interoperable with the alliance and recognizing its efforts to reform political and economic systems since the previous summit in Lithuania.

They pledged to support Ukraine on "its irreversible path to full Euro-Atlantic integration, including NATO membership."

But they also said NATO will be in a position to extend an invitation to Ukraine to join the alliance only when the current members "agree and conditions are met."

The leaders will hold a meeting with NATO's four Indo-Pacific partners -- Australia, Japan, New Zealand and South Korea -- on Thursday.

In the document, the leaders said they will boost practical cooperation with the four countries, including through projects related to Ukraine, cyber defense, disinformation and emerging technologies.

Related coverage:

NATO to launch 4 new defense projects with Indo-Pacific partners

Japan, South Korea leaders meet to discuss North Korea

North Korea fires 2 ballistic missiles, 1 possibly fails