On Monday, Russia turned on the taps on for a US$55 billion pipeline that will pump natural gas to the energy-hungry Chinese market – the latest step in the “new era” of increasingly close ties between the two countries. Presidents Xi Jinping and Vladimir Putin marked the occasion by getting together via video link and exchanging the usual pleasantries. But beyond the warmth and talk of expanding cross-border business, the two countries are being driven together by a common enemy: the United States. For that reason, relations are expanding beyond broader economic ties to deeper security cooperation, and analysts say that may eventually develop into some form of military alliance. In a meeting with Russian security council secretary Nikolai Patrushev in Beijing later on Monday, the Chinese leader made his concerns clear. “The United States and some other Western countries have increased their interference in the internal affairs of China and Russia, threatened the sovereign security of the two countries, and impeded their economic and social development,” Xi said. He said that China and Russia must cooperate to “safeguard their core interests and the common security of the two countries, and maintain regional and world peace and stability.” The opening of the gas pipeline comes amid four days of security and law enforcement meetings between the two countries this week in Beijing. The gathering is the first of its kind since China and Russia declared earlier this year that they had moved into a “new era” of bilateral relations. The cooperation will range over many sectors and industries, including energy, trade, technology, diplomacy and defence. This is cutting edge stuff now that Russia is starting to export Paul Dibb By any measure, the gas pipeline project is massive. It will pump 38 billion cubic metres (1.1 trillion cubic feet) of gas into China each year when it reaches full capacity. The pipeline will be operated by the Russian state-controlled energy company Gazprom, which said the 30-year deal to supply China – worth an estimated US$400 billion – is the biggest contract in its history. The two countries share one of the world’s longest land borders, stretching from a delta feeding the Sea of Japan to the steppes of Mongolia around 4,200km (2,600 miles) away. The border separates two economies that seem a natural fit, with Russia’s vast energy reserves and ample farmland able to help meet the needs of China’s growing economy and 1.4 billion people. Both countries have been reluctant to use the word “alliance” when discussing their security relationship, because the term is at odds with China’s current foreign policy. But military and political analysts said the increasing level of collaboration has put them on track to develop ever-deeper military ties. They point to Washington as the common denominator, with Russia still labouring under US sanctions following the annexation of Crimea in 2014, while China’s relations with America have come under increasing strain as a result of the trade war and the US reaction to the situation in Hong Kong and Xinjiang. Russia and China should be allowed to join G7, says Putin Zhang Xin, an associate professor at the school of advanced international and area studies at East China Normal University, said the “new era” in relations between Moscow and Beijing was “related to a vision of a quite significant change in the basic balance of power in the world”. The US is supposed to be on the decline and China is on the rise, but the US is also exerting more and more pressure toward both China and Russia”. He said: “In this regard, the security collaboration is, if not completely, at least partially a response to this context.” It’s their natural response to come together to face this potential threat from the US Artyom Lukin As a sign of this increased cooperation, China took part in a major Russian military training exercise in September for the second year in a row, and then the following month Putin announced that Moscow would help its neighbour develop an early-warning missile defence system . “Until recently, Russia was supplying military equipment [to China] that was not the very best of the Russian equipment, but it was good enough and better than the Chinese equipment,” said Paul Dibb, emeritus professor of strategic studies at the Strategic & Defence Studies Centre of the Australian National University. “But now we see Putin supplying modern quiet submarines, modern supersonic anti-ship missiles, and he has offered to build a ballistic missile warning centre for China – this is cutting edge stuff now that Russia is starting to export.” Observers agree that this relationship may evolve beyond training exercises and arms sales to mutually opposing any US or Western military activities that are perceived as a threat – for example, on the Korean peninsula, or in Eastern Europe. “If this trend continues for another five or seven years, probably by the late 2020s, we could see something that could be properly called a de facto military alliance between China and Russia,” said Artyom Lukin, a researcher with the School of Regional and International Studies at the Far Eastern Federal University in Vladivostok. “Both Moscow and Beijing see the United States as their common adversary, as the superpower whose military primacy threatens both Russia and China. So it's their natural response to come together to face this potential threat from the US,” he said. Vladimir Putin says Russia is helping China build a missile early warning system These perceived threats go beyond the military sphere to include what Moscow and Beijing regard as US interference in domestic affairs. This is of acute importance to China as it grapples with an ongoing popular protest movement in Hong Kong and in Russia as Putin’s rule continues to be punctuated by demonstrations against government corruption. From the viewpoint of Moscow and Beijing, such events bear similarities to the pro-democracy Arab spring and the so-called colour revolutions in the former Soviet Union, which they believe were instigated by the West, said Raffaello Pantucci, a senior associate fellow at the Royal United Services Institute, an independent British defence and security think tank. “Moscow and Beijing are both stable authoritarian [governments] and they don’t want to get overthrown by democratising masses, and that concept and that analysis of the world ultimately binds them together,” Pantucci said. However, he noted that under the surface there were differences between the two that could lead to fissures further down the line – for example, China’s increasing presence in Central Asia, an area Russia considers part of its sphere of influence . Discussions such as those being held about security and law enforcement this week suggest Russia and China may move beyond diplomatic and “symbolic” statements of support towards more tactical discussions, said Lukin. That could include, for example, Russia offering Beijing advice on countering popular movements like the protests in Hong Kong, he said. On an international level, the relations could then evolve into a “coordinated campaign by two authoritarian anti-Western powers” that leads to more military cooperation and even a disruption of the balance of power in the Indo-Pacific, said Dibb. Sino-Russian military days are increasingly becoming a topic of conversation in the US and Australia and it is likely that other regional players such as Japan are also studying developments closely. “There’s a sense of confidence from both [Russia and China] that it’s their time now, with a weak and a distracted West,” said Dibb. “Both have been successful at careful territorial salami slicing,” he said, referring to “the slow militarisation” of the South China Sea and Russia’s invasion of Georgia in 2008 and Ukraine’s Crimea and Donbass regions five years ago. “So the question is, what’s the next move?”