The success of Aung San Suu Kyi’s latest trip to Washington may mark a new chapter in Myanmar’s relations with the United States but the ongoing civil war in the country gives China control over crucial levers of pressure on its neighbour that the distant superpower can hardly match.

The warm welcome democracy icon Suu Kyi received in Washington reflects the US administration’s perception of Myanmar as one of its most significant foreign policy successes.

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When Barack Obama became president in 2009, Myanmar was still an international pariah, shunned by the West for its abysmal human rights record and subjected to economic and diplomatic sanctions imposed by the US and the European Union. Myanmar’s only really close ally at that time was China.

But much water has flowed down the Irrawaddy since. In a remarkable turnaround, a military-backed quasi-civilian government, which took over from the former junta in March 2011, started a process of rapprochement with the West and began to harden its stance towards China. This policy shift was exemplified by the suspension in September that year of a Chinese-funded hydroelectric power project at Myitsone in northern Myanmar and a gradual easing of political controls that led to a landslide election victory for Suu Kyi’s National League for Democracy in November.

But Myanmar remains of huge economic and strategic importance for China. It is its outlet to the Indian Ocean, and oil and gas pipelines have been built from the coast to Yunnan ( 雲南 ) province. Apart from Myitsone, there are other China-sponsored hydroelectric power projects, for instance on the Salween River. As a result, China is playing a complex diplomatic game in Myanmar.

China’s key role in helping Aung San Suu Kyi reconcile Myanmar’s decades-long ethnic conflicts

On the one hand, it has unleashed a charm offensive, promising to build hospitals and improve Myanmar’s crumbling infrastructure, and hosting Suu Kyi last month. But where there is a carrot, there is also a stick. And that stick is the United Wa State Army (UWSA), Myanmar’s most powerful ethnic armed force that controls a large swathe of territory along Myanmar’s northeastern border with China.

The UWSA sprung out of the army of the now defunct Communist Party of Burma (CPB), which was supported by China in the decade between 1968 and 1978. Chinese arms dealers have supplied the UWSA with an array of weapons that the old communists could never have dreamt of.

“The provision of a range of new weapons systems – surface-to-air missiles, armoured vehicles, howitzers and even helicopters – appears effectively to have turned the UWSA into a cross-border extension of the People’s Liberation Army,” said Anthony Davis of IHS Jane’s.

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“Even in the context of China’s large-scale military support for the CPB in the late 1960s and the 1970s, what has happened in the last few years is unprecedented.”

And, as another military analyst, who preferred to remain anonymous, asserted, the military equipment the UWSA had got from China was not of the kind that could “fall off the back of a truck” or be obtained on some local black arms market.

The UWSA’s latest acquisition, in 2014, was a large number of Chinese FN-6 portable air defence systems that are effective up to 3,500 metres and have been used effectively by Syrian rebels.

Few observers, however, believe that China would want the UWSA to actually go to war against the Myanmar government, but the equipment in its arsenal serves as a deterrent and will make the Myanmar military hesitate to launch an offensive against the force.

The UWSA is also a reminder of the fact that China, unlike the US, is Myanmar’s immediate neighbour and has the means to interfere in its internal conflicts – and that it can step up the pressure if Myanmar moves too close to the US.

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When in 2013 local people demonstrated against a Chinese-run copper mine project in Letpadaung in central Myanmar, Aung Min, a government minister told the protesters: “We don’t dare to have a row with China! If they are annoyed with the shutdown of their projects and resume their support of the communists, the economy in the border areas is doomed. So you better think seriously.”

At the same time, China, not the West, is the most important player in the country’s peace process, or talks between the government, the military and the country’s abundance of ethnic armies, which began under the former quasi-civilian government and has continued under Suu Kyi’s. The West’s participation has been mostly through hordes of private and official peacemakers who have achieved little more than turning their involvement into a lucrative industry.

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China, on the other hand, has sent its special envoy for Asian affairs, Sun Guoxiang, to talk, often in private, with all the players. He has also attended more formal and informal talks than any other foreign interlocutor. According to Davis: “Far more than any other foreign states supporting the peace process – notably Norway, Switzerland, the EU and Japan – China has vital strategic and economic interests at stake which will be fundamentally affected by either the shape of a future settlement or by continued war.”

The peace talks that Suu Kyi organised last month were not a success. The UWSA sent a delegation but they walked out when they learnt they had been classified as “observers”. It is unclear if that was their own decision, or did so at China’s behest. Delegates from ethnic groups who spoke on condition of anonymity believe the latter was the case.

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Nice words about enduring friendship and progress in implementing democracy and respect for human rights may have been said during Suu Kyi’s visit to Washington. But realities on the ground will not change. China is there, just across the northeastern border. And the US, despite its “pivot”, is far away.

Bertil Lintner is the author of Burma in Revolt: Opium and Insurgency since 1948 and Aung San Suu Kyi and Burma’s Unfinished Renaissance