The only rule dictating America's foreign policy and intelligence strategy is this: that it is beneficial to their foreign interests. All ethics aside, that is the one criterion.
As for trusting Pakistan, I would not. The ISI have been double-crossing the USA since they arrived in Afghanistan 10 days after 9/11. There is a reason that the USA cannot launch successful drone strikes *and* tell the Pakistanis - it is because every time they do, the targets disappear. It's been going on for years. However, I have no doubt the USA would do that if in a similar position; it's just about interests.
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