Energy Secretary: If U.S. 'Undermines' Iran Deal, 'It's Not Going to Be a Very Good Day After'

“I would say that today it’s about 2 months probably to assemble the nuclear material for a nuclear weapon and for the first 15 years it’s going to be substantially longer,” he responded.

“Breakout time means that if they were to kick out the inspectors and say, ‘we’re not following the agreement, all of you get out of here, we want to race to him a bomb,’ that it would still take them a year to get there with enough material,” he added.

Moniz also said converting the material into a weapon, such as a long-range missile delivery system, is not easy.

“A very key part of the agreement is that Iran forever is not allowed to pursue a whole set of activities called weaponization activities so even if you had the material you need to be able to make metal. You need to be able to have an explosively driven neutron source,” he said.

Moniz stressed the agreement does not mean the U.S. government can relax.

“We have to implement – we have to carry all of this through and it’s a big job but we’re going to do it,” Moniz said, adding that he has not heard a “credible” alternative to the current deal.

“I just haven’t heard it and I do know, as we said earlier, that if we are the ones who unilaterally undermine this agreement, it’s not going to be a very good day after. Again, it’s hard to imagine that we would not lose the unity of the international collaboration,” he said.