Obama has rejected the Pentagon's first draft of the "nuclear posture review" as being too timid, and has called for a range of more far-reaching options consistent with his goal of eventually abolishing nuclear weapons altogether, according to European officials.
Those options include:
Reconfiguring the US nuclear force to allow for an arsenal measured in hundreds rather than thousands of deployed strategic warheads.
Redrafting nuclear doctrine to narrow the range of conditions under which the US would use nuclear weapons.
Exploring ways of guaranteeing the future reliability of nuclear weapons without testing or producing a new generation of warheads.
The review is due to be completed by the end of this year, and European officials say the outcome is not yet clear. But one official said: "Obama is now driving this process. He is saying these are the president's weapons, and he wants to look again at the doctrine and their role."
The move comes as Obama prepares to take the rare step of chairing a watershed session of the UN security council on Thursday. It is aimed at winning consensus on a new grand bargain: exchanging more radical disarmament by nuclear powers in return for wider global efforts to prevent further proliferation.
That bargain is at the heart of the nuclear non-proliferation treaty, which is up for review next year amid signs it is unraveling in the face of Iranian and North Korean nuclear ambitions.