"China's Xi Jinping and Russia's Vladimir Putin on Thursday pledged a 'new era' of partnership between the two most powerful rivals of the United States, which they cast as an aggressive Cold War hegemon sowing chaos across the world."

Russia, waging war against NATO-supplied Ukrainian forces, and China, under pressure from a concerted US effort to counter its growing military and economic strength, increasingly have found common geopolitical cause.

Xi has told Putin the two have the chance to drive changes the world has not seen in a century, which many analysts see as an attempt to challenge a US-led global order.

Their governments, pushing back against perceived humiliations of the 1991 Soviet collapse and centuries of European colonial dominance of China, have sought to portray the West as decadent and in decline, with China challenging US supremacy in everything from quantum computing and synthetic biology to espionage and hard military power.

But China and Russia face their own challenges, including a slowing Chinese economy and an emboldened and expanding NATO following Russia's invasion of Ukraine.

Washington casts China as its biggest competitor and Russia as its biggest nation-state threat.

The US views both as authoritarian rulers who have quashed free speech and exerted tight control at home over the media and the courts. Biden has referred to Xi as a "dictator" and has said Putin is a "killer" and even a "crazy SOB." Beijing and Moscow have scolded Biden for the comments.