By Nectar Gan and Ben Westcott, CNN
Updated 0014 GMT (0814 HKT) June 17, 2021
Russia and China couldn't stop boasting about their "unbreakable friendship" ahead of Vladimir Putin's summit with US President Joe Biden this week.
Relations between Moscow and Beijing are at an "unprecedentedly high level," Russian leader Putin told NBC in an interview aired Monday, stressing he does not consider China a threat. "China is a friendly nation. It has not declared us an enemy, as the United States has done," he said.
On Tuesday, Beijing returned the praise in kind, declaring the "sky is the limit" for bilateral cooperation. "China and Russia are united like a mountain, and our friendship is unbreakable," Foreign Ministry spokesperson Zhao Lijian told a news briefing.
In recent years, the two countries have gravitated closer toward each other amid their deteriorating relations with the West. For Russia, a pivot to the world's second largest economy was a natural solution to sanctions over its annexation of Crimea and incursions into eastern Ukraine in 2014. And Beijing was more than happy to embrace closer ties with its northern neighbor as tensions escalated in almost every aspect of its relations with the US.
Economics has been at the center of their strategic partnership. Bilateral trade passed $100 billion in 2018, and the goal is to double it by 2024. The two countries have also deepened energy cooperation, including a $400 billion deal to transport natural gas from Russia and multiple joint nuclear power plant projects in China. Moscow is also Beijing's largest arms supplier, providing 70% of China's arms imports between 2014 and 2018. On the diplomatic front, Beijing and Moscow have often sided with each other at the United Nations Security Council, countering the US and its allies on issues such as Syria while rejecting Western criticism over human rights violations.
But their tactical alliance has taken on more urgency since Biden came into office with a pledge to assert US leadership on the world stage. Under Biden, Washington has repeatedly singled out Russia and China as the biggest threats to the rules-based international order, as it rallies allies to unite in an apparent ideological battle between democracy and autocracy.
Over the past few days, discussions on how to counter the authoritarian actions of Russia and China were featured prominently in both the Group of Seven (G7) summit in England and the NATO meeting in Brussels.
In response, Moscow and Beijing have presented a strong united front against the criticism, as well as what they say are "attempts at destroying" their relationship.
"We have to tell those who try every means to drive a wedge between China and Russia that any attempt to undermine China-Russia relations is doomed to fail," Zhao, the Chinese Foreign Ministry spokesperson, said on Tuesday.
But despite the show of unity, plenty of potential for friction remains.
Trade relations between the two countries are deeply imbalanced. China is Russia's largest trading partner, while Russia is a far less significant trading partner to China. The majority of Russia's exports to China comprise of natural resources and raw materials, in exchange for imports of manufactured goods.
There could be geopolitical concerns too. Through its Belt and Road Initiative, China has expanded its economic influence in Central Asia, an area long deemed by Russia as its sphere of influence.
Beyond official relations, the Russian public is growing increasingly wary of Chinese investment in Siberia and the Russian Far East, where Chinese projects have stoked resentment and backlash from locals.
Observers have long seen growing Sino-Russian ties as a partnership of convenience driven by geopolitical and economic interests, after the two powers moved on from their past animosity. In the late 1950s, relations between Moscow and Beijing became strained, and were later characterized by deep mistrust, ideological disputes and border conflicts.
And now, in the absence of shared fundamental values, common ideologies and a formal military alliance, it remains to be seen just how deep and lasting their ties will be.