Glad I don't have to make this call, but assuming there is substantial evidence that Posada was behind the airline bombing, I'd send him to Guyana, and simply announce that the U.S. doesn't believe he'd get a fair trial in Venzuela or Cuba.
Once he's in Guyana, they can do with him as they wish.
"Senor Posada, we don't like Castro either, but nor do we like terrorists who blow up airliners."
Owl_Eagle
(If what I just wrote makes you sad or angry,
it was probably sarcasm)