Russia and China declared their deepening alliance on Wednesday after the US warned against any Chinese military involvement in the war in Ukraine.
Meeting senior figures in Moscow, China's most senior diplomat Wang Yi said Beijing was "ready to strengthen our strategic partnership and our in-depth co-operation".
The alliance "does not give in to pressure", he said.
Russian Foreign Minister Sergey Lavrov said the two countries were ready to "defend each other's interests" during a period of "high turbulence on the world stage".
President Vladimir Putin said the partnership was "very important to stabilise the international situation", almost a year since Russia invaded Ukraine.
Mr Putin subsequently addressed a rally at Moscow's Luzhniki Stadium, where he paid tribute to doctors, families of soldiers and others supporting the war effort.
"When we are protecting our interests, our people, when we are protecting our language, culture, our territory – everyone, all of our people, are defenders of the motherland,” he said.
The meetings came a day after rival speeches by Mr Putin and Joe Biden, in which the US President framed the war in Ukraine as a struggle for democracy against autocracy.
Although he did not mention China, the tense relations between Washington and Beijing are under renewed pressure over alleged Chinese spying.
US Secretary of State Antony Blinken claims to have information that China is considering arming Russia in the conflict in Ukraine, which Beijing denies.
"That would be a terrible step, but not only from our perspective, from the perspective of many other countries in Europe and beyond," he said on Tuesday.
China has taken a cautious line on the conflict, siding with Russian talking points that blame Nato expansion for the war, but calling for peace talks and warning Moscow against any nuclear escalation.
It has supported Russia economically by strengthening trade ties and shunning western sanctions, but is not known to have provided weapons.
Mr Wang, who met Ukrainian officials at last week's Munich Security Conference, said China was seeking to “promote mutually beneficial co-operation in all areas”.
Another western official said on Tuesday that there was no indication yet of China providing arms, which he said would be a major policy shift.
"China, so far, has not shown any interest in sustaining the war," the official said. "It would be a significant escalation to actively support Russia with lethal aid."