The US has warned Iran that it will not tolerate interference with the Strait of Hormuz. Only 34 miles wide, 40 percent of the world's tanker-borne oil passes through it. Closure of the strait would wreak havoc on global oil markets. Angry over the threat of new sanctions, Iranian leaders have upped their rhetoric in recent days, claiming that closing the waterway would be as easy as drinking a glass of water. With pressure growing again on Iran over its nuclear program, amid warnings of new sanctions, what's the agenda being pursued by Iranian leaders? How is the oil market responding? Is this a serious sign of increasing tensions in the region?