The new treaty is designed to follow the Kyoto protocol, the world's existing treaty to regulate greenhouse gases, the first phase of which expires in 2012.
Concluding this treaty would be a real achievement for Mr Obama - but it would follow three previous nuclear disarmament deals and it would not visibly alter the balance of power in the world.
Meanwhile the promises made by the NPT's members to stand by the treaty will likewise count for nothing without the will to hold to account Iran, Syria and the others that may follow them.