Spectacular diplomatic boil-over between US, Iran

There's been a spectacular diplomatic boil-over between Iran and the United States with Tehran warning Washington that it faces "the mother of all wars" if the US threatens the nation's oil exports. The US Secretary of State rushed to his country's defence, and President Trump fired back, tweeting a warning to Iran never to threaten the United States again, or suffer consequences". Our correspondent in Washington DC is Kate Fisher. She talks to Guyon Espiner.