Nuclear Attack on Iran?

The latest from Drudge is that someone in the Pentagon leaked to Sy Hersh our war plans to attack Iran's budding nuclear capability using nuclear weapons. Hersh became famous as an investigative journalist who broke the story on the 1969 My Lai massacre during the Vietnam War.

So how would the U.S. strike deal a death blow to Ahmedinejad's nuclear weapons program? Part of the alleged plan would be to attack Iran's main centrifuge plant at Natanz, 200 miles south of Teheran. U.S. Strategic Command would likely employ a USAF B-2 bomber armed with the B61 mod 11. The B61-11 can penetrate the earth several meters before it detonates its thermonuclear payload. The yield of the B61-11 physics package is classified, but some suggest it is the same as the maximum yield of the B61 mod 7, which is 370 kilotons.

Here are some links:
Story in Britain's Telegraph
Info on B61 nuclear bomb from Wikipedia
Fact sheet on B-2 Spirit from af.mil
U.S. Strategic Command