When a US warship recently sailed near a Chinese-controlled artificial island in the South China Sea, it signalled the White House was finally taking a tougher stance on Chinese behaviour in the waters.

Beijing described the move as an illegal incursion into the waters around Subi Reef, which is also claimed by Taiwan, the Philippines and Vietnam. Washington labelled it a freedom of navigation exercise that was aimed at demonstrating that the US does not recognise Chinese claims in the area.

But following months of debate inside the Obama administration, the White House had actually chosen the option that involved the least provocative actions by the US Navy, partly to avoid antagonising China too much ahead of a climate change conference in Paris where Chinese co-operation will be crucial.