The USA knew about Pakistan's nuclear programme during the 1980s but cut off aid only in 1990. Why then?
- In the 1980s the USA needed Pakistan as its ally against the Soviet forces in Afghanistan, so aid continued.
- Soviet troops left Afghanistan in 1989.
- Once Pakistan was no longer needed in that war, the nuclear issue came first and aid was stopped.
Answer: The end of the Afghan war removed the USA's reason to overlook the nuclear programme.