China’s exclusion from – and Vietnam’s inclusion in – this summer’s Rim of the Pacific naval exercise (Rimpac) is not just a diplomatic snub – it’s the kind of slight that could have deep and dangerous geopolitical repercussions. The US-led Rimpac, which started in late June and lasts until early August, is a biennial military exercise often referred to as the world’s largest war game. This year, it brought together the navies of 26 nations for exercises spanning a huge swathe of ocean from the Hawaiian islands to southern California.

It offers a unique opportunity for militaries from Pacific Rim countries to train and work together to maintain peace and stability in the region. Also, the games are seen as a way of ensuring open access to important shipping lanes in the western Pacific’s increasingly contested waters.

Washington has framed its decision to “disinvite” the Chinese navy from the exercise as a response to China’s militarisation of the South China Sea. In recent months, China has deployed electronic warfare equipment and surface-to-air missiles to the Spratly Islands, and it has, for the first time, landed a strategic bomber on Woody Island in the Paracels.

In the lead-up to the 2016 Rimpac, the Obama administration had considered disinviting China due to its construction of artificial islands in the Spratlys. The islets are contested by Beijing and six others, including Taipei, though an international tribunal has ruled against Beijing’s claims.

Snubbed in world’s biggest war game, will Beijing make waves in South China Sea?

This year’s games come amid rising US-China tensions. Last month, President Xi Jinping told visiting US Secretary of Defence James Mattis China would not give “an inch of territory” in the Pacific Ocean. Earlier in June at the Shangri-La Dialogue in Singapore, Mattis said there would be “much larger consequences” in response to China’s installation of military infrastructure on disputed islands.

By contrast, Vietnam’s first participation in Rimpac is a sign of strengthening military relations between former foes, as both Washington and Hanoi see each other as a counterbalance to China’s push for dominance in South China Sea, where Hanoi is also a claimant.

With China out and Vietnam in, the US is signalling a change of direction in its military relations. This gives diplomatic observers good reason to speculate that the US is fortifying a political coalition in the region with an aim to contain China’s rising clout and assertiveness.

The US began hosting Rimpac in 1971 as a means of assuring allies the US withdrawal from Vietnam did not herald a withdrawal from Asia. From the US perspective, Rimpac brings together a constellation of allies to conduct operations in support of sustained US influence in the region. Most participants, including the UK, Germany, France, Canada, Japan, India and Australia, endorse the US assertions of freedom of navigation. Four claimants in the South China Sea – Brunei, Malaysia, Indonesia, and the Philippines (but not Taiwan) also participate in Rimpac.

Washington’s “snub” of China when it comes to Rimpac comes amid growing fears that smaller Asian nations cannot stand up to Chinese pressure and are unable to influence Beijing. It’s worth noting many of these countries were once in the hands of imperialist powers, including Chinese emperors, and endured brutal struggles for independence.

What’s behind Beijing’s South China Sea moves?

Washington wants to maintain the regional balances of power that have maintained stability under a US-sponsored security order. In recent policy statements, Washington has defined China as a revisionist power that intends to reshape the regional order and security arrangements.

The latest developments are a reminder that a confrontation between the US and China is increasingly possible. Washington and Beijing must decide how much risk they are willing to take to dominate the world’s most important sea lanes. But if Beijing’s increasingly assertive foreign policy results in the creation of a regional US-led, anti-China coalition, it could prove to be China’s biggest diplomatic failure in decades. ■

Cary Huang, a senior writer with the South China Morning Post, has been a China affairs columnist since the 1990s