John Kerry actually said...

The best estimate was 2 to 3 months.

If Congress votes to disapprove and manages to override the President's veto, it would very likely dismantle the agreement.

This is not something that President Obama just sort of dreamed up and thought was a good idea.

I think it far more likely that were the United States to turn down the JCPOA, we would find ourselves in a far worse position.