Yesterday, Navy Adm. Michael G. Mullen, chairman of the Joint Chiefs of Staff, told CNN interviewer John King that he thinks Iran has enough fissile material to make a nuclear bomb. He said:

“We think they do, quite frankly.”

Meanwhile, on NBC, Defense Secretary Robert Gates apparently said the opposite:

“They’re not close to a stockpile, they’re not close to a weapon at this point

Politico noted the discrepancy.

What’s going on here?

The LA Times story about the interviews mentions a recent IAEA report finding that Iran has a bit more than a ton of “enriched uranium.” Additionally, the Wisconsin Project on Nuclear Arms Control estimates that Iran actually had enough of this particular “low enriched uranium” to make a bomb by December 2008 and will have enough for a second one in October 2009.

As Mark Kleiman clarifies on his blog, however, low enriched uranium is not the same substance as highly enriched uranium (HEU), which is the weapons-grade material needed to make a bomb (without plutonium anyway).

In his 2005 Nuclear Terrorism book Graham Allison explained (see pp. 99-100) that it would take a substantial effort using a cascade of 1500 centrifuges operating for about one year to yield the 35 to 100 pounds of HEU that a state would need to manufacture a single nuclear bomb. The state needs the smaller amount only if it has mastered the technology and developed a beryllium reflector. Otherwise, it needs the larger amount.

Iran currently has close to 4000 centrifuges operating at the Natanz facility (and is heading to 6000), which means they could theoretically create HEU in months. However, the IAEA and the world would notice that kind of enrichment — at least at Natanz.

Granted, the technical barriers to an Iranian bomb are falling, but some stories about Mullen’s remarks definitely make it sound as if Iran has made a political decision to construct a bomb. After all, this is the sentence following the one I quoted above:

And Iran having a nuclear weapon I’ve believed for a long time is a very, very bad outcome for the region and for the world.”

Yet, there’s no publicly available evidence that Iran has moved to make a bomb.

The late 2007 NIE said

We judge with high confidence that in fall 2003, Tehran halted its nuclear weapons program.

My blog post from that time quoted additional skepticism from the NIE.

Arms Control Wonk has been complaining about the panicked reporting on Iran’s technical achievements for some time.

The different apparent messages from Gates and Mullen certainly suggest that the administration is not trying to sell an Iran war to the American public. Or, if they are, they’re not as good at it as the Bush people were.