MOSCOW (BLOOMBERG) - Chinese President Xi Jinping and his Russian counterpart, Mr Vladimir Putin, will have more than vodka shots and gifts of ice cream to show for their warming relationship when they meet this weekend on the sidelines of a developing nations' summit in India.

Recent months have seen greater security cooperation between Russia and China as they find common ground against the US. The neighbouring giants last month held their first joint naval drill in the South China Sea and both have condemned US plans to deploy a US missile shield in South Korea.

A Russian general said this week the military was working with China to counter an expansion of US missile defences, which they see as upsetting the balance between the three nuclear powers.

"The fact that both countries started to talk about joint actions on the military level is a very serious development," said Mr Vasily Kashin, a senior fellow of Russian Academy of Science's Far Eastern Studies Institute. "The threat from US missile defence pushes both China and Russia closer to each other. For Russia and China, the policy of containment is the containment of the US first of all."

The moves show how the rapport between Mr Xi and Mr Putin - as shown by frequent visits and personal gifts - has begun to foster more formal security ties. Their planned encounter on the sidelines of the Brics summit in the Indian resort region of Goa would be their fourth this year and their 19th one-on-one meeting since Mr Xi took power 2012.

China saw a surge in Russian ice cream sales last month after Mr Putin brought some for Mr Xi, and Mr Putin told China's state broadcaster they celebrated his birthday in 2013 by drinking vodka shots "like two college students".

The development of those ties has coincided with a decline in both nations' relations with Washington. Russia has provided powerful backing for China's efforts to challenge the US' long-standing security dominance in the Asian-Pacific region.

Lieutenant General Viktor Poznikhir, of the Russian Armed Forces General Staff, said computer command staff from the two countries conducted a missile-defence exercise this year to counter a successful deployment of a US missile shield.

"We are working together on ways to minimise possible damage to the security of our countries," Lt Gen Poznikhir told a security forum in Beijing on Tuesday (Oct 11), adding another exercise was planned for next year.

US Democratic presidential nominee Hillary Clinton said in a private speech in 2013 she warned Chinese officials while secretary of state the US would "ring China with missile defence" if they didn't curb North Korea's nuclear weapons programme, according to what appears to be an internal campaign document among hacked e-mails released by WikiLeaks last week.

The target of the attack, Clinton campaign chairman John Podesta, on Tuesday refused to confirm the veracity of the e-mails, saying the FBI was investigating the breach. Mrs Clinton's aides have suggested that the e-mails might have been fabricated or doctored. They blame Russia's government for the leaks, as does the US government, while Russia has denied responsibility.

China, meanwhile, backed Russia's failed United Nations resolution last weekend that would've urged a ceasefire without a halt to the bombing of Aleppo. It abstained from a competing French-drafted proposal that sought an end to air strikes and military flights over the besieged city.

"We cannot choose our neighbours and this is a good thing," Mr Putin said on Wednesday (Oct 12) in Moscow at a business forum. "Over these last decades, we have developed quite unique relations of trust and mutual support."

International security issues will feature when Mr Xi and Mr Putin meet, Chinese officials said at a briefing on Monday (Oct 10) in Beijing. "China and Russia hold the same position on the most important international and regional issues, including on Syria and Afghanistan," Vice Foreign Minister Li Baodong said.

Russia was China's largest supplier of foreign oil in August. That relationship has helped make China its top trading partner and provided an economic lifeline to Mr Putin. A recovery in oil prices helped lift two-way trade by 3.6 per cent year on the year in the first quarter, according to China Customs figures, after plunging 29 per cent to US$68 billion (S$94.3 billion) last year.

"I definitely think this energised cooperation is significant, but fundamentally, Russia and China will put their own interests first," said Ms Sarah Lain, a research fellow at the London-based Royal United Services Institute who specialises in Russia's ties to world powers. "They will support each other on things that are of mutual interest, which is usually aimed at demonstrating an alternative power base to that of the US."

Building security ties with Russia requires Mr Xi to revise China's long-standing opposition to foreign entanglements and comes as he boosts his country's peacekeeping role in Africa and wades into Middle Eastern issues.

China and Russia signed a joint statement during Mr Putin's visit to Beijing in June, pledging to strengthen "global strategic stability". What remains to be seen is whether China would be willing to give Russia greater support in areas where it has relatively few interests, such as Syria and Ukraine, and risk upsetting its Western trading partners.

China deployed its first special envoy for the Syrian crisis in March and sent a delegation led by a senior military official there in August for talks with Syrian and Russian officials.

Mr Zheng Yu, a senior researcher with the Chinese Academy of Social Sciences' Institute of Russian, Eastern European and Central Asian studies, said the country would maintain a balanced approach toward Syria.

"We've told Russians that China is only a global economic power, but not a geopolitical superpower yet," Mr Zheng said. "We only selectively wade in on international hot-spot issues. The Middle East for China is still an unfamiliar battleground of global players."