http://news.bbc.co.uk/2/hi/americas/3530358.stm

This article from The New Republic helps to put things into context.

Key quote from the article:

... a White House aide told ul-Haq last spring that "it would be best if the arrest or killing of [any] HVT were announced on twenty-six, twenty-seven, or twenty-eight July" -- the first three days of the Democratic National Convention in Boston.