Xi and Putin in May 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.
"At present, the world is going through changes unseen in a hundred years, the international situation is intertwined with chaos," Xi told Putin in the Russian city of Kazan at the opening of the BRICS summit.
"But I firmly believe that the friendship between China and Russia will continue for generations, and great countries’ responsibility to their people will not change."
Russia, waging war against NATO-supplied Ukrainian forces, and China, under pressure from a concerted U.S. effort to counter its growing military and economic strength, increasingly have found common geopolitical cause.
Russia and China, 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.
The United States casts China as its biggest competitor and Russia as its biggest nation-state threat, and President Joe Biden has said the democracies face a challenge from autocracies such as China and Russia.
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.
Putin called Xi "dear friend" and said the partnership with China was a force for stability in the world.
"Russian-Chinese cooperation in world affairs is one of the main stabilising factors on the world stage," Putin said.
"We intend to further enhance coordination on all multilateral platforms in order to ensure global security and a just world order."
Xi said cooperation in the BRICS group was "the most important platform for solidarity and cooperation between emerging market countries and developing countries in the world today."
He said it was "a mainstay force in promoting the realization of equal and orderly global multipolarity, as well as inclusive and tolerant economic globalisation."
