China and Russia closely cooperate on civilian nuclear plants.
Russian President Vladimir Putin will travel to China this week to meet Xi Jinping, the Kremlin chief's first trip outside the former Soviet Union this year.
What are the five things to watch for at the meeting?
Defence Bosses
As Defence Minister Li Shangfu has not been seen in public for more than six weeks, China watchers will be looking at who takes the lead in any talks with Russian military officials on cooperation.
Li was sanctioned by the U.S. in 2018 for an arms deal he secured with Russia in an earlier role. General Liu Zhenli, the head of the military body responsible for China's combat operations and planning, has emerged as the top contender for the job.
For China, Russia is a not only a major source of oil and gas: the world's biggest nuclear power is also a rich potential source of technology as the People's Liberation Army (PLA) seeks to modernise its conventional and nuclear forces by 2035.
Russian aviation, rocket and even submarine technology has been shared over recent decades with China, according to a 2022 assessment by the U.S. Department of Defence.
China and Russia closely cooperate on civilian nuclear plants - some of which could be used to produce military grade plutonium, such as the fast breeder rectors at Xiapu.
Weapons for War?
China has refrained from condemning Russia's operation against Ukraine or calling it an "invasion" in line with the Kremlin which casts the war as "a special military operation".
The United States has warned China against sending any weapons to Russia, though China is the second largest importer of Russian crude after India and thus supports Russia's economy.
China has denied reports in Western newspapers that it has sent weapons to Russia.
Best Friends?
Both Putin and Xi like to project a close friendship: Putin once delivered Russian ice creams - Chistaya Liniya's "Eskimo" and "Plombir" - to Xi on his birthday while Xi is the only world leader to have celebrated Putin's birthday with him.
During a 2019 visit to Russia where both leaders signed off a package of trade deals and admired pandas at Moscow zoo, Xi told Russian media: "President Putin is the foreign colleague that I have interacted with most extensively. He is my best friend, and I greatly treasure our friendship."
Xi also awarded Putin a friendship medal in 2018, saying that "Putin is my best close friend".
Putin said in March that he had invited Xi to his private apartment in the Kremlin. He said they had a fireside chat over tea.
Oil And Gas?
The heads of Russian energy giants Gazprom and Rosneft, Alexei Miller and Igor Sechin, will join Putin's retinue during his visit to China, sources familiar with the plans have told Reuters.
Russia wants to secure a deal to sell more natural gas to China and plans to build the Power of Siberia-2 pipeline, which would traverse Mongolia and have an annual capacity of 50 billion cubic metres (bcm).
That compares to the 38 bcm the currently operational Power of Siberia is expected to reach by 2025.
The proposed pipeline would bring gas from the Yamal peninsula fields in western Siberia to China, the world's top energy consumer and a growing gas consumer. The price has yet to be agreed.
Soaring Trade?
Trade between Russia and China soared 30% in the first half of this year and will rise to more than $200 billion in 2023, Russian Economy Minister Maxim Reshetnikov said on a visit to China.
Russia is now China's second largest trade partner outside Asia, second only to the United States, which accounted for half a trillion in trade in the first nine months of this year. Russia accounted for $176 billion and Germany $158 billion.
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