NATO Secretary-General Jens Stoltenberg on Monday called for China to face consequences for what US officials have called a major export push to rebuild Russia's defence industry.

China presents itself as a neutral party in the Ukraine war, and says it is not sending lethal assistance to either side, unlike the United States and other Western nations.

On Tuesday Beijing said NATO "should engage in self-reflection rather than arbitrary smears and attacks on China".

Domestically, Russian President Vladimir Putin has framed the 2022 invasion as a defensive move against an expanding NATO.

"We advise (NATO) to stop shifting blame and sowing discord, not add fuel to the fire and instigate confrontation, but rather do something practical for the political settlement of the crisis," Chinese foreign ministry spokesman Lin Jian said at a regular press briefing.

China and Russia's strategic partnership has only grown closer since the invasion of Ukraine, but Beijing has rebuffed Western claims that it is aiding Moscow's war effort.

It has however offered a critical lifeline to Russia's isolated economy, with trade booming since the conflict began.

And G7 foreign ministers on Friday expressed "strong concern" about transfers of dual use materials and weapons components from Chinese businesses to Russia being used by Moscow for its military expansion.

China steered clear of a weekend summit in Switzerland promoted by Ukrainian President Volodymyr Zelensky that reaffirmed Kyiv's demands for Russia to leave Ukrainian territory for any peace to be won.

Chinese President Xi Jinping "has tried to create the impression that he is taking a back seat in this conflict, to avoid sanctions and keep trade flowing," Stoltenberg said Monday on a visit to Washington.

"But the reality is that China is fuelling the largest armed conflict in Europe since World War II," he said, warning that "at some point... there should be consequences".

NATO next month celebrates its 75th anniversary with a summit in Washington that aims to send a decisive long-term message of support for Ukraine ahead of President Joe Biden's re-election fight against Republican candidate Donald Trump.

"The more credible our long-term support, the quicker Moscow will realise it cannot wait us out," Stoltenberg said.

"It may seem like a paradox, but the path to peace is more weapons for Ukraine," he said.