Iran has formulated a plan codenamed "Muddy Waters" to block oil traffic in the Strait of Hormuz by steering a tanker onto rocks and causing a massive oil spill, Der Spiegel reports. Iran's co-operation would be needed to clean the spill, as would a temporary lifting of the embargo on the country. The speculation comes as the EU considers tougher sanctions on Iran, which has reiterated an offer to suspend domestic production of medium-enriched uranium.