Adherence to the NPT is no obstacle to an agreement. The roadblocks will come from Israel -- which is not a party to the Treaty -- the Gulf monarchies, the Republicans (and some Democrats) in Congress, and the alliance between the neo-conservatives who successfully pushed for the war in Iraq and Afghanistan, and the powerful American Israel Public Affairs Committee.
A close reading of the NPT is something everyone can do. The document is only four and a half pages and its language is accessible to anyone. In contrast, wading through the 53-page "Comprehensive Nuclear Test-Ban Treaty," a document certainly as important as the NPT, is an ordeal. But a close reading of the NPT is not necessarily comfortable for the governments of the U.S., China, France, Britain, or Russia. In particular Article VI:
"Each of the parties to the Treaty undertakes to pursue negotiations in good faith on effective measures relating to the cessation of the nuclear arms race at an early date and to nuclear disarmament, and a Treaty on general and complete disarmament under strict and effective international control."