That would let Congress, controlled by Trump's fellow Republicans, effectively decide whether to kill the deal. With no evidence Iran is violating the deal in any way, he is going to instead claim it is just "not in the national interest of the United States" to honor the deal's terms.
Asked whether the administration had considered that possibility, Sanders said: "I think we've been very clear what our position is on the deal.
And I've said many times, we can not let the Iranian relationship be defined exclusively by that nuclear agreement".
Iranian officials have strongly suggested that they would abandon the agreement or at least no longer feel bound by its nuclear limitations.
That hasn't persuaded Trump. Only the reimposition of pre-JCPOA sanctions, approved by Congress or enforced by executive order, would have the effect of "withdrawing" the USA from the agreement.
Citing an unidentified official in Washington, Reuters reports that Trump is preparing to roll out a broader USA strategy on Iran that would be more confrontational.
Mattis hinted his boss may try to decertify without breaking the deal.
European ambassadors speaking in Washington last week said they would do everything possible to protect companies based in Europe and that continue to do business with Iran from reimposed US sanctions.
Trump has often railed against the Obama-era deal, which offered Iran massive sanctions relief in return for curbs on its nuclear program.
One would involve Trump grudgingly certifying Iran's compliance a final time and then persuading Congress to change the law so he wouldn't have to do so again. Corker declined yesterday to discuss prospects for action on the Iran accord.
In doing so, the president must verify that Iran is transparently adhering to the deal- and that the continued suspension of nuclear-related sanctions are in the national security interest. But the decision must come by an October 15 deadline.
Trump has to announce every 90 days whether Iran is in compliance.
That's been a concern since Trump first started campaigning on withdrawing from the deal.
The administration's approach may help assuage European allies, who have privately expressed a willingness to work on other ways to control Iran as long as the United States agrees to remain in the nuclear deal.