The U.S. is in violation of the NPT.
TREATY ON THE NON-PROLIFERATION OF NUCLEAR WEAPONS
Entered into force March 5, 1970
Each of the Parties to the Treaty undertakes to pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a Treaty on general and complete disarmament under strict and effective international control.
news report, Sep 15, 2012:
The U.S. nuclear arsenal, the most powerful but indiscriminate class of weapons ever created, is set to undergo the costliest overhaul in its history, even as the military faces spending cuts to its conventional arms programs at a time of fiscal crisis.
There is no official price tag for the effort to upgrade and maintain the 5,113 warheads in the inventory, to replace old delivery systems and to renovate the aging facilities where nuclear work is performed. A study this summer by the nonpartisan Stimson Center, a Washington think tank, estimated costs would be at least $352 billion over the coming decade to operate and modernize the current arsenal. Others say the figure could be far higher, particularly if the work is delayed even longer.