With missile batteries, fleets of attack boats and stocks of naval mines, Iran can disrupt traffic through the Strait of Hormuz but probably cannot completely shut down the world's most important oil route, military analysts say. The question for Iran's leadership is whether it is worth the heavy price.
Trying to close the strait would bring down a powerful military response on Iran's head from U.S. forces in the Gulf and turn Tehran's few remaining international allies against it.
That Iran is making such dire threats at all illustrates its alarm over new sanctions planned by the U.S. that will target oil exports - the most vital source of revenue for its economy. Iran's leaders shrugged off years of past sanctions by the U.S. and United Nations, mocking them as ineffective. But if it cannot sell its oil, its already-suffering economy will be sent into a tailspin.
"It would be very, very difficult for Iran even to impede traffic for a significant period of time," said Jonathan Rue, a senior research analyst at the Washington-based Institute for the Study of War. "They don't have the ability to effectively block the strait."
What the Iranians can do, Rue and other analysts said, is harass traffic through the Gulf - anything from stopping tankers to outright attacks. The goal would be to panic markets, drive up shipping-insurance rates and spark a rise in world oil prices enough to pressure the United States to back down on sanctions.
The strait would seem to be an easy target, a bottleneck only about 30 miles across at its narrowest point between Iran and Oman.
Tankers carrying one-sixth of the world's oil supply pass through it, from the fields of petrogiants Iran and its Gulf Arab neighbors, exiting the Persian Gulf into the Arabian Sea and on to market. They move through two two-mile-wide shipping lanes, one entering the Gulf, one exiting.
In recent years, Iran has dramatically ramped up its navy, increasing its arsenal of fast-attack ships, anti-ship missiles and mine-laying vessels. Still, those forces would not likely be enough to outright seal the strait, given the presence of the U.S. 5th Fleet based in the Gulf nation of Bahrain. On Wednesday, Pentagon spokesman George Little warned that any "interference with the transit or passage of vessels through the Strait of Hormuz will not be tolerated."