NATO chief Jens Stoltenberg said Wednesday China was sustaining Russia's economy in the face of Western sanctions over the Ukraine war, as the alliance frets over closer Beijing-Moscow ties.

NATO foreign ministers held talks in Brussels with Asia-Pacific partners Japan, South Korea, Australia and New Zealand over the growing challenge from China.

"China refuses to condemn Russia's aggression. It echoes Russian propaganda. And it props up Russia's economy," Stoltenberg said.

"At a time when Beijing and Moscow are pushing back against the rules-based international order, it is even more important that we continue to stand together."

The call for a unified stance came as French President Emmanuel Macron arrived in Beijing to speak with Chinese leader Xi Jinping.

Macron said in the Chinese capital that anyone helping "aggressor" Russia in its war on Ukraine would be viewed as an "accomplice".

But he also said Beijing can play a "major role" in finding a path to peace in Ukraine and insisted Europe must not "disassociate ourselves from China".

Stoltenberg reiterated Western warnings to China not to supply weaponry to Moscow's struggling forces in Ukraine.

He said that so far NATO had "not been able to confirm" that Beijing was making any arms deliveries to Russia.

"China knows that there will be severe consequences" if it does so, he warned.

Stoltenberg said he had invited the leaders of the four Asia-Pacific partners to NATO's Vilnius summit in July as the alliance looks to boost its links with the region.