Iran's official news agency says the country's Revolutionary Guards have opened a new naval base on the Persian Gulf. It is the fourth in a string of Revolutionary Guards bases along the waterway. The elite force was put in charge of defending Iran's Gulf coast in September. Tension over Iran's nuclear program prompted the Guards' commander to threaten in June to seal off a key oil route through the Gulf's Strait of Hormuz in the event of an attack by Israel or the US Forty percent of the world's oil transits the passage. Monday's IRNA news agency report says the new base is in the port of Assalouyeh. It will control a 300-kilometer stretch of coastline west of the strait between Kish Island and the port of Dayyer.