The recent release of an audiotape by Bin Laden offering a truce in the war may be used to kick off the election year season of ratcheting up the fear of terrorism.
In his message bin Laden points to attacks in other countries and promises a new attack on the US and explains the reason for not doing so earlier:
As for the delay in carrying out similar operations in America, this was not due to the failure to breach your security measures. Operations are in preparation, and you will see them on your own ground once the preparations are finished, God willing.