BEIJING, China – China stressed on Monday that the friendship between Beijing and Moscow was still "rock solid", despite international condemnation of Russia's ongoing invasion of Ukraine, as Beijing said it was open to helping mediate peace.

China has refused to condemn its close ally Moscow after only last month touting a "no limits" strategic partnership between the two countries.

"The friendship between the two peoples is rock solid, and both sides' future cooperation prospects are very vast," said Foreign Minister Wang Yi at a press briefing during the Chinese leadership's annual political congress in Beijing.

But he said China was "willing to work with the international community to carry out necessary mediation, when necessary".

The European Union's foreign policy chief Josep Borrell said last week that China should mediate future peace talks between Russia and Ukraine as Western powers cannot fulfil the role, in an interview with Spanish daily El Mundo.

Beijing has repeatedly said it would play a "constructive role in calling for negotiations" to resolve the crisis, but has not previously committed to joining or hosting any peace talks.

Wang also said China would send humanitarian aid to Ukraine.

- Economic ties -

The foreign minister described the China-Russia relationship as "the world's most crucial bilateral relationship", which "is conducive to world peace, stability and development".

He referred to last month's China-Russia partnership commitment as "clearly and unmistakably showing the world" that both countries "jointly oppose the revival of the Cold War mentality and stoking ideological confrontations".

This month, Russian gas giant Gazprom said it had signed a contract to design a pipeline to China, taking a step towards a new supply agreement that could ease Russia's reliance on European buyers.

And Russian banks said Sunday they planned to issue cards using China's UnionPay system after Visa and Mastercard moved to suspend operations amid unprecedented sanctions on Moscow.

Once bitter Cold War rivals, China and Russia have moved closer than ever since President Xi Jinping took power nearly a decade ago, driven by their shared desire to confront US power.

Wang said their informal alliance would "not brook interference by third parties", in a warning to the United States and its Western allies who in recent days have lobbied China to play a more active role in mediating the conflict.

Australia's prime minister has called Russia's invasion of Ukraine "a moment of choice for China", pressing China to shape the actions of its Russian ally and prove that Beijing is committed to global peace.

"No country would have a greater impact right now on Russia's violent aggression towards Ukraine than China," Scott Morrison told think tank the Lowy Institute.

Analysts have speculated whether Russia's invasion would embolden China to take similar military action towards the self-ruled island of Taiwan, which Beijing claims as its own territory.

But Wang said the "Taiwan issue is fundamentally different from the Ukraine issue" and added that Taiwan will "eventually return to the motherland's embrace".

"Taiwan is an inalienable part of China's territory and the Taiwan issue is entirely China's internal affair," Wang Yi said.

"The Ukraine issue is a dispute between the two countries of Ukraine and Russia."