NOW THAT NORTH KOREA has called America's diplomatic bluff by testing a nuclear device, and the wrangling has begun over how best to sanction Pyongyang, the question arises of what's in store for Iran. Will we bomb? Some insiders say yes, that President Bush has already decided that if Iran fails to freeze its enrichment program, he will direct our Air Force to attack Iran's nuclear plants sometime before he leaves office.

The urgency for bombing, of course, turns on the assumption that we can know precisely when Iran will acquire its first nuclear weapon--which we can't.  A decision to bomb also presumes we can set Iran's nuclear weapons program back significantly with a single targeting campaign. This, at best, is unclear. Iran, for instance, might have a parallel, hidden nuclear weapons effort. Given Teh ran's ability to tunnel a kilometer deep, and its stonewalling on what it has done with the advanced uranium enrichment plant designs it bought and claims it chose not to build, there's cause for concern. No bombing campaign is likely to destroy Iran's nuclear engineers. Whatever plants we destroy, they can rebuild.

A decision to bomb should turn less, then, on when we think Iran will "go nuclear" (something we are sure to get wrong) or how effective our first strike might be (also a matter of uncertainty) than on what we and Iran are likely to do with the time such a strike might conceivably buy. Although there's some confusion about what we might do--bomb indefinitely or persuade

First, since February, senior Iranian officials have repeatedly warned that Iran would retaliate against any U.S. strike by blocking the Strait of Hormuz. All oil shipped from the Persian Gulf on tankers exits through this channel. If successful, such a move would choke off international access to roughly 40 percent of the world's oil exports--an economic disaster for every oil importer worldwide.

Second, we know Tehran is willing to use terrorist proxies against Israel, Iraq, the United States, and any of its friends.

Finally, Iran has threatened to withdraw from the Nuclear Nonproliferation Treaty and to block further international nuclear inspections if it is sanctioned or otherwise prevented from exercising its "inalienable right" to make "peaceful" nuclear fuel. If Iran were to do this, a cascade of proliferation--starting with Saudi Arabia, Egypt, and Turkey--could easily commence.

The United States and its friends could hedge against these threats, and should already be doing so. The first move is to reduce the vulnerability of energy exports from the Persian Gulf. Oil experts have determined that all but the 2 to 3 million barrels a day that Iran itself ships through the Strait of Hormuz could be piped instead to ports on the Red Sea and the Sea of Oman. Pipelines from Iraq, past Kuwait, through Saudi Arabia to the Red Sea, the UAE, and Oman are already in place; they only need to be connected.

This could be done by reopening the Iraqi pipeline across Saudi Arabia that the Saudis seized from Saddam in 2001, and by having anti-drag agents (chemical additives that increase the flow of existing oil pipelines as much as 60 percent) at the ready. It also would require building relatively short spur lines to integrate Omani and UAE pipelines with the Saudi pipeline system (something now under discussion). Most of this project could be completed in roughly 18 months for less than a billion dollars. In addition, it would be useful to build up a stock of oil on ships at sea as a floating reserve. This could provide a supply cushion for several weeks, allowing a smooth transition to moving oil by pipe rather than through the strait.