Eight days of war games between the giant neighbours, who share a 4300km border, also present a commercial opportunity for Russia, China's biggest supplier of arms and weapons technology, to flog its wares, analysts say.
"The main target is the United States. Both sides want to improve their position for bargaining in terms of security, politics and economics," said Jin Canrong, a professor of international relations at the People's University of China.
Both countries say "Peace Mission 2005", which involves 10,000 troops and army, navy and air force exercises, is aimed at building ties between their militaries, and analysts say it is not targeted at any third country.
"Military cooperation is linked with political and economic cooperation as part of a bigger package," said Robert Karniol, Asia-Pacific editor for Jane's Defence Weekly. "It's not an adversarial posture."
The two countries say they seek
to boost cooperation
But with the drills also helping to "strengthen the capability of the two armed forces in jointly striking international terrorism, extremism and separatism", according to China's Xinhua news agency, they are likely to be viewed with concern by others in the region.
The word separatism will give pause for thought to the residents of Taiwan, the self-governed island China claims as its own and which it has vowed must return to its rule - by force if necessary.
Once Cold War foes, ties between Beijing and Moscow have been growing closer, in part due to China's efforts to tap into Russian energy resources to feed its booming economy. The two are also players in six-party talks on North Korea's nuclear crisis, reflecting shared security interests.
Russia and China also see common ground in Central Asia, both in trying to ensure political turmoil in Uzbekistan and Kyrgyzstan does not spill into their borders, and in checking the US presence in the region.
Russia and China want to check
the US presence in the region
After last year's "Orange Revolution" in Ukraine, when demonstrators propelled a pro-Western government to power after street protests against rigged elections, Russia took the initiative to upgrade the scale of the exercise with China, Jin said.
In July, the Shanghai Cooperation Organisation (SCO), a regional security forum grouping China and Russia with the Central Asian states, told US-led troops to fix a date for their departure from military bases in the region.
Message to Washington
That, along with the fact observers from other SCO countries will be at the war games, is further fuelling theories that they are intended to send a message to Washington.
"This is above all an assault on the uni-polar world that has so suited Washington since the end of the Cold War," Russian daily Nezavismaya gazeta said.
The United States said the exercises supported a shared goal of regional stability, but added a word of caution.
"The main target is the United States"
Professor, People's University of China
"We would hope that anything that they do is not something that would be disruptive to the current atmosphere in the region," US State Department spokesman Sean McCormack said.
The exercises are taking place in the Russian Pacific near Vladivostok and in the Chinese coastal province of Shandong and run through 25 August.
With China gradually overhauling its military, streamlining troop numbers and buying high-tech weapons platforms from abroad, the war games are more likely to result in a shopping spree than any aggressive posturing.
Analysts say rather than cause alarm, the exercises should also be seen as making both militaries behave with more transparency and in line with international norms.
"I think they finally figured out it might be useful to learn something from other people," Karniol said of China.