The transatlantic military alliance NATO has for the first time described China as presenting a "serious challenge".
It claimed Beijing was working to undermine the global order and expressed concern about how fast the country is developing nuclear missiles.
NATO leaders were meeting in Brussels on Monday. It was Joe Biden's first summit as US president and he sought to convince allies of Beijing's threat.
Jens Stoltenberg, NATO secretary-general, said: "China is rapidly spreading its nuclear arsenal with more warheads and a larger number of sophisticated delivery systems. It is opaque on implementing its military modernisation and it is cooperating militarily with Russia, including through exercises in the Euro-Atlantic area."
Stoltenberg also referred to the online threat posed by China, as well as in its growing sphere of influence in Africa and Europe's own technological infrastructure, such as 5G technology.
"China is coming closer to us," he added. "We see them in cyberspace, we see China in Africa, but we also see China investing heavily in our own critical infrastructure. We need to respond together as an alliance."
But Stoltenberg was keen to point out Beijing is not NATO's enemy and that there are mutual issues like climate change that they can work together on.
"We're not entering a new Cold War and China is not our adversary, not our enemy... we need to address together, as an alliance, the challenges that the rise of China poses to our security," Stoltenberg said.
Not every leader appeared to be sold on the threat posed to NATO by China though.
French President Emmanuel Macron told reporters following the meeting: "NATO is a North Atlantic organisation. China has nothing to do with the North Atlantic."
"We shouldn't bias our relationship with China. It is much larger than just the military... we shouldn't distract away from the many challenges we have within NATO," he added.
China wasn't the only issue of concern for the alliance, however.
Russia received significantly more mentions in the organisation's statement - 61 compared to Beijing's 10, suggesting that Moscow is still thought of as representing the more clear and present danger by NATO.
Stoltenberg described relations with the Kremlin as at their lowest point since the Cold War and that Russia’s aggressive actions constituted a threat to Euro-Atlantic security.
German Chancellor Angela Merkel made it clear also that Russia still presented the greatest threat, saying that "Russia, above all, is the major challenge” for NATO.
This was part of Biden's first trip abroad as the US president, who earlier described NATO as "critically important for US interests".