US threats are not the way to protect the Philippines' interests in the South China Sea

International law, not the language of war, is the key to calming these choppy waters

Philippine President Rodrigo Duterte greetingUS Secretary of State Mike Pompeo at Villamor Air Base south-east of Manila. AP

Over the weekend, US Secretary of State Mike Pompeo was in Manila. While there, he affirmed, for the first time publicly, that the US would defend by force the Philippines' sovereignty over its areas of the South China Sea.

The South China Sea dispute is hugely consequential, even though it appears recently to have fallen off the agenda, owing to the Trump administration’s focus on North Korean disarmament. But rather than threatening the Chinese militarily, the US has another, possibly more effective option of “diplomatic containment”. This strategy could pull Beijing closer, via strict adherence to smaller sets of agreements and laws. Firing a verbal shot across China's bows in such troubled waters is a risk.

The South China Sea is vigorously contested. Around a third of global sea trade passes through it, and every regional country has an interest in what happens above and below its waves. It hosts vast oil and gas reserves, so the precise demarcation of national maritime boundaries matters a great deal. China claims roughly 90 per cent of the waters, falling within an ill-defined arbitrary “nine-dash line” that has no international legal standing.

For decades, the US has patrolled the region, maintaining “freedom of navigation” patrols. In recent years, however, China has become increasingly assertive, threatening fishing vessels and heavily militarising small disputed islets and reefs. However, there has not yet been an uncontainable flashpoint.

In Manila, though, Mr Pompeo warned that “any armed attack on any Philippine forces or public vessels in the South China Sea will trigger mutual defence obligations”. Countries such as the US, a Chinese foreign ministry spokesman replied, “should not make waves when there is no wind”.

Fortunately, it seems that the threat is actually too serious to be credible. Neither the US, China, nor the Philippines, which has prioritised its economic links with China, want any such confrontation.

The US could also tie China up in the international legal system. Take, for example, the 2016 ruling by an international tribunal in The Hague on Beijing's territorial rights. The Philippines took China into arbitration, claiming that Beijing was interfering with its rights in its exclusive economic zone – the areas up to 200 nautical miles from Philippines territory. The hearing found overwhelmingly in favour of Manila, concluding that there was “no legal basis” for China's nine-dash line. China has refused to recognise the ruling, and the Philippines has not wanted to escalate the issue. But the US could, and should pressure Beijing to fall in line.

Then there is the simmering dispute around the remote islands of Natuna. Indonesia, although only tangentially involved in the South China Sea dispute, has been pushing back at Chinese encroachment around this archipelago that lies north-east of Singapore. Last week, an Indonesian minister announced that the country would develop fisheries around the islands, using high-tech equipment such as drones and satellites to help Indonesian fishing boats. For years, Indonesian and Chinese vessels have clashed in the area, with Indonesian warships even firing on Chinese trawlers, and destroying smaller boats. Further build-up would increase the likelihood of a clash.

Here, again, the US should encourage and assist Indonesia in protecting its economic rights. Indonesia is one of the few south-east Asian countries able to stand up to China, and with help from the US, the Natunas could set a precedent.

But perhaps the best diplomatic stance that the US could take would be to support Vietnam, where the US-North Korea summit took place last week, and the nation’s attempts to get a code of conduct for the 10-nation Asean bloc rewritten. A leaked draft at the end of last year suggested that Hanoi was pushing strongly to outlaw some of China’s most controversial activities, particularly the deployment of missiles and the militarisation of disputed islands.

But China has its own negotiating stance, and the leaks suggest that Beijing wants a ban on any military drills with outside powers (meaning the US), unless all Asean countries agree (which, of course, China won't). Here, the US can shore up support for the other, smaller, Asean countries in this crucial negotiating period. If a code of conduct could be agreed that curbed even some of China's activities in the area, it would have a significant impact on peace in the South China Sea.

To do that, however, the US would have to persuade south-east Asian countries that it will not be an unreliable ally; that it will, in the event of future conflict with China, be there to support them. Disputing this, China's premier Li Keqiang quoted a Chinese proverb at the most recent Asean meeting in November: “Better a near neighbour than a far relative.”

Rather than making military threats and forcing countries such as the Philippines to make uncomfortable choices, the US should support regional efforts to entangle China in international legislation. After all, the last thing the region needs is for these waters to get any choppier.