Simon Jenkins calls for the U.S. to respond to this week's letter from Tehran. He concludes:

"There is, of course, one thing that Britain and America could do that would wholly disorientate Ahmadinejad and have him rushing troops to his borders. It would be a sudden end to the occupation of Iraq and Afghanistan. Such a decision would remove at a stroke the running theme of Iranian militancy. It would saddle Tehran with two unstable neighbours whose insurgents and revanchists would cause it, its allies and its surrogates no end of trouble. After a bit of initial crowing the next Iraq will be Ahmadinejad's nightmare. Unfortunately such a step seems too clever by half for the west's present leadership."