From al-Qaeda operative "Rakan Ben Williams"; translated via MEMRI :
"I discern your wonder about this warning in which you do not quite recognize what to make of it. You are probably asking: Why would Al-Qaeda Organization announce its upcoming operations inside the mainland? Why the repeated warnings?
However, coming from Al-Qaeda, a disclosure like this reflects one thing and one thing alone: full faith and trust in Allah.
"You ought not to be intolerably upset; for whoever survives this upcoming blow will have a probability to learn an amazing lesson in the art of conducting 'expeditions.'
Let me also inform you that we are talking about two operations, not one. The scale of one of them is larger than the other but both are large and significant. However, we will start with the smaller, and temporarily put the larger on hold to see how serious the Americans are about their lives. Should you value your own life and security, accept Muslims’ demands, but if you shall prefer death (over giving in to Muslims’ demands). Then, we, by the grace of Allah, are the best in bringing it (death) to your door steps.
"Let me now inform you why we opted to inform you about the two operations and your inability to stop them before they are carried out. The reason is simple; you cannot uncover or stop them except by letting them be carried out...
"This is the last warning you will receive from us. Consequently, if you ignore it, we regret to inform you that we will carry out devastating operations against the States of America and we will not show mercy whatsoever, you would have brought destruction to yourselves.
Sounds like Rakan is claiming to have two nuclear devices already implanted in US cities; awaiting bin Ladin's orders to detonate. There is no way of knowing if any of the above threats have a grain of truth in them, except the lines bolded above - surrender to Islam, or we will slaughter you.
Bring it on, Rakan...every hear of Mutual Assured Destruction?
Michelle Malkin has an analysis of who Rakan Ben Williams might be here.