Recently declassified US documents has confirmed that Americans tried to stop Pakistani nuclear program in 1970s. Declassified documents show that then-Secretary of State Cyrus Vance ordered American diplomats to use all means to stop Pakistan nuclear program.
Then US Secretary of State Cyrus Vance said, "We believe it is critical to stability in the region and to our non-proliferation objectives to inhibit Pakistan from moving closer to the threshold of nuclear explosive capability."
Despite these efforts by the US, Pakistan successfully tested its nuclear weapons in 1998 in response to tests by India. Today, Pakistan has over 100 nuclear weapons along with number of ballistic missiles and cruise missile to deliver them.