With 110 pounds of HEU, it'd be trivial. With only 37 pounds, it is within our technological capacity...but not theirs.
What the other person failed to note is that a 12.5 kilton bomb could not "level Manhattan" unless it was detonated above Manhattan. If detonated on the ground, the explosive force would be considerably reduced.
Did anyone ever find that passenger jet that was stolen about a year ago? I think it could get far enough above Manhattan, or any other city, to maximize the effect.
Only in the movies. Working with such brittle, dangerous metals as Uranium is anything but trivial, as are creating the proper nuclear "trigger" and core shape, all of which are affected greatly by the decay of the different elements and their introduction (through decay) of impurities into the whole process.
Likewise, the electronics and conventional explosives used to start the detonation are all impacted negatively by the emitted radiation of the fissionable material, among other such problems.
Consider that NAZI Germany couldn't figure out how to overcome these hurdles during WW2, though not for lack of trying. Neither could Soviet Russia or the UK at that time, either. Then consider that most of the Middle East considers WW2-era V-2 (ooops, SCUD) missiles to be state of the art.
So there is considerably more to building an actual nuclear bomb than meets the eye, though a dirty bomb *is* a trivial task.
Of course there just MIGHT be three shipments... 37 Lbs X 3 = 111 LBs = BOOM!
What the other person failed to note is that a 12.5 kilton bomb could not "level Manhattan" unless it was detonated above Manhattan. If detonated on the ground, the explosive force would be considerably reduced.
Above is not so difficult if you have suicide pilots again.
Or suicide elevator operators...