The two most powerful men in the world oil market appeared together in Houston on Tuesday to tell the world that their strategy was on track. In December, Khalid al-Falih and Alexander Novak, the energy ministers of Saudi Arabia and Russia, orchestrated a 24-nation plan to cut oil output in the first half of 2017. This week they spoke to reporters in a hotel conference room at the annual CERAWeek energy conference to emphasise their commitment to the pact. Despite their reassurances, the US oil price suffered its sharpest one-day sell-off for 13 months on Wednesday, and has fallen by 7 per cent over the week. After months floating sideways, West Texas Intermediate crude is now trading below $50 for the first time since December. The impression of price stability, created by three forces: Opec, hedge funds and shale oil producers in the US, now appears misleading and augers further volatility for the industry. While Mr Falih described compliance among the Opec members and other parties to the production cut agreement as “very satisfactory,” the oil market was jolted on Wednesday when government data showed that crude stocks in the US had climbed a ninth straight week to a new record.