The price of oil has dropped sharply after a meeting of oil producers failed to agree a cap on output. The meeting in Qatar was attended by most members of oil producers' group OPEC, including Saudi Arabia, except Iran. Saudi Arabia, the world's biggest exporter, had been prepared to freeze output if all Opec members had agreed. But, Iran is continuing to increase output following the lifting of sanctions against it. After hours of talks in Qatar, the country's Energy Minister Mohammed bin Saleh al-Sada said that the oil producers needed more time. The next scheduled OPEC meeting is in June.