Washington, DC – Senate Foreign Relations Chairman Robert Menendez (D-NJ) sparred with Secretary of State John Kerry at a hearing on Tuesday over ongoing nuclear negotiations with Iran that are, by many accounts, making significant progress towards a resolution.

As nuclear negotiations between Iran and world powers recommenced in Vienna, Menendez took issue with reports that the parties planned to begin drafting an agreement as early as May that would place constraints and transparency measures over Iran’s nuclear program, but would not “dismantle” the program completely.

Many expect a final deal will allow Iran to retain a closely monitored civilian nuclear program while lengthening the amount of time it would take Iran for “break out” for a weapon to as long a period as possible, likely in the range of six to twelve months.

“I don’t think that we did everything that we’ve done to only get a six to twelve month lead time,” said Menendez, who has in the past has argued that the U.S. should demand that Iran completely dismantle all enrichment capabilities. More recently, Menendez has authored Congressional letters that have been presented as offering more flexibility on the enrichment issue in a bid to attract broader support among colleagues. But at the hearing, he offered his most recent such letter as evidence that the Senate would accept a deal allowing enrichment. He expressed incredulity that “a deal that would ultimately unravel the entire sanctions regime for a six to twelve month lead time is not far from where we are today.”

Kerry pushed back, arguing that a deal that lengthens Iran’s breakout to six or twelve months would be “significantly more” than the current timeline. He explained that the United States believes Iran’s current breakout timeline is about two months—meaning that Iran could eject inspectors and enrich enough uranium for one nuclear weapon in that time, but still would not have a warhead or delivery system for a nuclear weapon. A deal would lengthen that period and, according to Kerry, implement inspections and transparency measures necessary to immediately detect any attempt to breakout for a weapon.

Kerry stressed, “At the end of this we hope to be able to come to you with an agreement that has the most extensive and comprehensive and accountable verification process that can be achieved in order to know what they are doing.”

Menendez appeared most concerned that such a deal would eliminate sanctions, and that Iran would be able to breakout faster than the U.S. could slap on new sanctions if such a move were detected. “With no sanctions regime in place and – understanding that every sanction we have pursued have needed at least a 6 month lead time to become enforceable, and then a greater amount of time to actually enforce that – the only option left to the United States, to this or to any other President and to the West would be either to accept a nuclear armed Iran or to have a military option,” he said.