While it is tempting to dismiss this letter as a loony bit of correspondance , THIS combined with the admission of the Speaker of the Iranian Majlis (Parliament) HERE as highlighted HERE suggests quite strongly that the message Iran is sending the U.S. and the world is that it is ready, willing and even eager to go to war.
Given the theocratic nature of that government, it cannot be assumed they will take decisions in a utilitarian manner.
And so the analysis suggests they might even be willing to start off the proceedings. I'm not sure about that but it cannot be ruled out.
If you are an investor and have not yet taken positions in gold, silver or oil this might be the time to do it.
UPDATE : Bush Letter to Ahmadinejad