The unpredictable US President Donald Trump has declared the ceasefire agreement with Iran over, not long after it began. At the same time, he has left the door open for US representatives to continue negotiations with Iran, even if he added: “I think they are wasting their time.” This follows fresh US air strikes on the Islamic republic after reported attacks on shipping in the Strait of Hormuz.Negotiations remain the only hope for a lasting settlement. China has led calls for a return to dialogue and the negotiating table amid concerns about damage to the global economy from uncertainty, not least about oil and gas shipments. About 20 per cent of the world’s oil supply passes through the strait.As war spreads in the region again through tit-for-tat retaliatory Iranian attacks on neighbouring Gulf states, the return of uncertainty is reflected in investor watchfulness of its effect on global markets.That said, the initial shock to economic indicators like energy prices and stocks was relatively contained, compared with the first outbreak of fighting followed by the blockade of the strait. How long that continues could depend on a quick return to common sense on both sides, restoration of the ceasefire, and freedom and safety of passage for commercial shipping in the strait.Hopes of the ceasefire and talks being put back on track sooner rather than later do not reckon with Trump’s unpredictability. When asked about the ceasefire on the sidelines of the Nato summit in Ankara, he said: “I think it is over. I don’t want to deal with them any more.”He also indicated he was considering reinstating the US naval blockade of Iran, saying: “We may put it back, the blockade, and it’ll only be a blockade for Iran.”