This interview with Ronald Spiers, former U.S. Ambassador to Pakistan contains.a bit on U.S. intelligence during the early 1980s on Pakistan’s nuclear weapons program. Asked “What was your evaluation of our intelligence on the Pakistani nuclear developments?,” Spiers replied as follows:

It was rudimentary; most of the information came from clandestine sources developed by the Embassy. But I must add that I didn’t know how much there was to know. It was very clear that there was a group in Pakistan that was working towards the development of a nuclear capability. We didn’t know how far it had advanced. We knew that they were not reprocessing plutonium at that point. We knew they were obtaining some technical assistance from the PRC—that was common knowledge in Islamabad. There was an installation near Islamabad which was off limits to everybody. Once, the French Ambassador had a picnic near this area and was jumped upon and brutally beaten up. It was clear to me that the Foreign Office, including the Foreign Minister—Jacub Khan — who by the way was one of the most competent people I had ever met, didn’t know anything about what was going on the nuclear field. It was not clear to me that even Zia’s principal nuclear advisor, Munir Khan, was fully cognizant of developments. The little group of nuclear experts was headed by A.Q. Khan, whom I never met because he lived in the south some place and was kept under-cover. Khan had worked once upon a time for EURENCO (European Uranium Enrichment Company) and had allegedly stolen or
had copied enrichment machinery plans. That was some evidence here and there of small procurement efforts which by themselves appeared innocent enough, but that if taken as a whole appeared to be part of a larger pattern. Once plans for a nuclear device had been purloined, the evidence became very strongly suggestive that the Pakistanis were embarked on the development of a weapons program. I am sure that Zia was well aware of what was going on.