Iran is poised to flood the market with another 1m barrels per day (bpd) of crude oil should it achieve a binding agreement to curb its nuclear programme by the next deadline on June30. Re-opening the Iranian spigots after years of nuclear sanctions will set up a monumental battle between the Islamic Republic and Saudi Arabia for control of the Organisation of the Petroleum Exporting Countries (Opec). It will also pile pressure on high-cost shale oil producers in the US who will struggle to compete with a tidal wave of Iranian crude which could hit the markets within months.