Amid its escalating conflict with Israel, in which the US has also now taken part by bombing three key nuclear installations, Iran has warned that it may take the unprecedented step of closing the Strait of Hormuz, the world's most critical oil corridor. 

Nearly 20% of global oil exports flow through the narrow waterway between Oman and Iran, and the closure of the Strait could put the transit of about 18 million barrels per day of oil and other fuels at risk. 

Iran has threatened to close the Strait of Hormuz several times but has never followed through because the country also relies on it to export most of its crude oil, along with other Organisation of Petroleum Export Countries (OPEC) members like Saudi Arabia, United Arab Emirates, Kuwait and Iraq.