Officials alleged that Islamabad has customized conventional Harpoon antiship missiles, which were provided to it by the Reagan administration as a defensive weapon in the cold war era.
"There's a concerted effort to get these guys to slow down. Their energies are misdirected," said one senior administration official.
The accusations come at a time when the Obama administration is pushing the Congress to approve 7.5 billion dollars in aid to Pakistan over the next five years.
It is also worth mentioning here that Washington, time and again, has asked Islamabad to focus more fighting the Taliban rather than expanding its nuclear and conventional forces against India.
According the New York Times, US officials made these accusations in 'unpublicized' diplomatic protest to Prime Minister Yusuf Raza Gilani and other top Pakistani officials in June.
The United States has also accused Pakistan of modifying American-made P-3C aircraft for land-attack missions.
However, Pakistan has denied the charge, saying it developed the missile itself.