Iran is talking about a move that could throw the global oil market into chaos. And this time, it is not just a political threat, it is halfway to being law. Iran’s parliament has approved a plan to close the Strait of Hormuz, a narrow stretch of water that carries nearly a fifth of the world’s daily oil supply. Iran is talking about a move that could throw the global oil market into chaos. And this time, it is not just a political threat, it is halfway to being law. Iran’s parliament has approved a plan to close the Strait of Hormuz, a narrow stretch of water that carries nearly a fifth of the world’s daily oil supply.