"We have a new one: Test but verify," he said.
"We're building the capacity to know exactly what is happening [in Iran] in an unprecedented fashion," he said. "We believe our hand is very strong."
Some members sitting on the dais had a different appraisal."It's looks like 'Grovel but verify' to me," said Rep. Dana Rohrabacher,
R-Calif., who objected to Kerry's referring to Ayatollah Ali Khamenei by his title, "supreme leader." The congressman described the senior cleric, believed to exert de facto control over all Iranian governance, as a vicious man with a bloody background. The deal Kerry signed in November stipulates the U.S. will not pass further sanctions against Iran. The House already passed legislation that would levy further sanctions, which the Senate is currently considering, and is weighing further options.
Experts in negotiating with Iran say such action would torpedo the deal.
Throughout Tuesday's hearing, Kerry claimed the sanctions already imposed were designed to bring Iran to the negotiating table and thus have worked.
"We were not imposing these sanctions for the sake of imposing them," said Kerry, a former Senate Foreign Relations Committee chairman before beginning his current job in February. "Has Iran changed its nuclear calculus? I honestly don't think we can say just yet. But we now have the best chance we've ever had to rigorously test this proposition."
"We will be the first ones to come to you, if this fails, to ask for additional sanctions," he added.
Rep. Theodore Deutch, R-Fla., said the sanctions were designed to get Iran to give up its nuclear program, not negotiate the terms for it.
House Committee Chairman Rep. Ed Royce, R-Calif., also questioned the Obama administration's de facto endorsement of Iran's "right to enrich" if the deal goes through.
"Iran, from our standpoint, does not need this technology to generate electricity," he said. "If they have this technology, it is exactly what they do need to make nuclear weapons."
Kerry claimed leaving the existing sanctions in place could prompt a Western war with Iran.
"If you're going to take a nation to war, you better have exhausted all possible ways of negotiating peacefully," he said. "There's nothing naive about what we're doing.""It may be wrong, you might find miscalculation, but it's not a miscalculation founded on naivete," Kerry added. "If we were just negotiating and pressing them further, we would be inviting a prolonged process. That would drive them to want to get a the weapon even more, and then you'd be at a place where you'd get a negotiation but they'd be closer to getting the weapon than they are today."