Russian President Vladimir Putin described relations with China as being at an "unprecedentedly high level," CNN reported.
Putin's statement comes after the two countries signed a long-delayed agreement to build a massive new pipeline to deliver natural gas to China through Mongolia.
Following a meeting in Beijing between Putin, Chinese leader Xi Jinping and Mongolian President Ukhnaagin Khurelsukh, Russian state energy company "Gazprom" announced that a legally binding agreement has been signed for the construction of the "Power of Siberia-2" gas pipeline.
According to analysts, the pipeline could compensate for nearly half of the gas exports to Europe that Russia has lost since the start of the war in Ukraine.
Gazprom CEO Alexei Miller explained that the deal includes a 30-year supply agreement, and the price will be lower than that charged to Europe.
After the meeting of the leaders of the three countries, Putin and Xi Jinping held their first official talks since the Russian leader arrived in China.
Recalling Soviet ties with China during World War II, Vladimir Putin welcomed "the memory of brotherhood in arms, trust, mutual support and firmness in defending common interests" as the basis for their countries' strategic coordination "in the new era".
"We were always together then and we remain together now", the Russian president addressed Xi Jinping at the beginning of their bilateral meeting.
For his part, the Chinese leader said that relations between Beijing and Russia "have withstood the test of changing international circumstances" and called Putin "an old friend". Xi Jinping expressed China's readiness to work together with Russia "to support mutual development and revitalization, firmly uphold international fairness and justice, and build a fair and reasonable system of global governance".