Sen. Bob Corker, the committee chairman, opened the hearing by firing some shots.
"Based on my reading [of the deal]," Corker said, "I believe that you have crossed a new threshold in U.S. foreign policy. Where now it is a policy of the United States to enable a state sponsor of terror to obtain a sophisticated, industrial nuclear development program that has as we know only one real, practical need."
Kerry fired back saying the deal had been reached between Iran and six world powers, who Kerry said "are not dumb."
"Let me underscore the alternative to the deal we've reached isn't a better deal – some sort of unicorn arrangement involving Iran's complete capitulation. That's a fantasy, plain and simple," Kerry said during his opening statements. "The choice we face is between a deal that will ensure Iran's nuclear program is limited, rigorously scrutinized, and wholly peaceful or no deal at all."
In broad terms, the deal reached between Iran and the U.S., Iran, Russia, China, U.K., France and Germany, curbs Iran's enrichment capabilities and in exchange lifts nuclear-releated sanctions put in place by the United Nations, Europe and the United States.
Kerry told Congress that at this point in history, Iran already has the knowledge to make enough fissile material to make a nuclear bomb.
"We can't bomb that knowledge away," Kerry said. "Nor can we sanction that knowledge away."
Moniz reiterated what the administration has been saying all along.
"To be clear, this deal is not built on trust," Moniz said. "It is built on hard-nosed requirements that will limit Iran's activities and ensure inspections, transparency, and verification."
Moniz added: "I can assure you that this is not what Iran wanted," because it dials back Iran's nuclear program significantly.