Straits of Hormuz
That was Greenspan's theory on Iraq, too.
You should know that the Conventional Wisdom on the Left is that Saddam's pitiful country in 2003 could not possibly have done anything to block the Straits. This came up quite frequently in discussions about Greenspan's elaboration on the "it was about oil" statement.
The Saudis are furiously constructing a huge network of pipelines that will, in a few years, allow most Middle Eastern oil to bypass the Straits. This hasn't been done to the extent it could have been, since the ships are more economical. One main pipeline used to run through Lebanon, and is no longer in use.