under the terms of secret agreements, U.S. personnel have been stationed in Pakistan whose sole function is to guarantee and secure the safety of Islamabad's nuclear arsenal and keep it out of the hands of terroristsThere is much more in the article about secret measures the U.S. has taken in Pakistan.
Along with Pakistan, the article also mentions Iran. Former CIA officials reveal that the U.S. has infiltrated the Iranian nuclear supply chain and has "been able to insert flaws into the technology that we can exploit." And here's the key quote:
"The point is that when they push the button, the stuff won't work," the former senior official said.Read the whole article. If true it is pretty reassuring, and reveals exactly the sorts of things that I hope our intelligence services are doing in secret.
He and others said that the operation "is fairly long-standing" and successful.