The heated rhetoric Beijing and Washington exchanged on the South China Sea in the lead-up to the region's premier security summit, the Shangri-La Dialogue, gave the impression that matters would come to a head at the annual forum. But the tone was markedly milder when People's Liberation Army deputy chief of General Staff Admiral Sun Jianguo and US Defence Secretary Ash Carter spoke at the three-day event in Singapore that ended on Sunday. Although both called for calm and a desire for peace, the delegates went home with tensions remaining high and the possibility of a mishap in the contested waters as real. Cooler heads are needed to lower the risks and that is best done through dialogue and negotiations. Positions were reiterated, with Carter painting China as a troublemaker for its land reclamation, while Sun emphasised sovereignty and the risks posed by American actions, which include strengthening military alliances with Chinese neighbours and a threatened deployment of military vessels. The commander of the US Pacific Command, Admiral Harry Harris, set the scene in Australia days earlier by referring to the turning of reefs into artificial islands as creating a "great wall of sand". But China, as Carter acknowledged, is not alone, with Vietnam and the Philippines long ago starting such work. With an American spy plane overflying the area on May 20, it is unsurprising that Beijing's latest defence white paper criticised Washington for "meddling". The South China Sea has become a friction point in the relationship, but both sides know of the dangers of escalating tensions. Toned-down words in Singapore reflected that; with important meetings coming up, ties have to be kept in check. The annual US-China strategic and economic dialogue will be held in Washington this month and President Xi Jinping makes an official visit in September. Both sides also have much to cooperate on, North Korea among them. China has to work with neighbours on a code of conduct. The US, with trade and investment interests, has to act constructively and responsibly.