Secretary of State John Kerry (R), Energy Secretary Ernest Moniz and Treasury Secretary Jack Lew defend their Iran deal at the Senate Foreign Relations Committee.

A better alternative to the current Iran nuclear deal is a “fantasy,” a fiery Secretary of State John Kerry told the Senate Foreign Relations Committee on Thursday.

In ongoing attempts to sell the international deal with Iran that has divided Congress, Kerry insisted that the current deal effectively closed known Iranian nuclear pathways to the bomb at its declared sites in Natanz, the underground Fordow facilities and the heavy water reactor in Arak.

If the U.S. rejects the deal it will be walking away from every restriction we have achieved, he said, and will be isolated diplomatically for letting an internationally agreed arrangement fail. He even suggested Gulf countries like Saudi Arabia have warmed up to the deal.

Kerry compared the alternative deals  that have been suggested — wherein access is provided to international inspectors anytime and anywhere, and sanctions on conventional weapons would remain in place — to a “unicorn arrangement” that was merely a “fantasy.”

He insisted that when the U.S. started negotiations with Iran the country had enough fissile material to build 10-12 nuclear weapons and had 19,000 centrifuges spinning, and that if the U.S. walks away from the deal Iran will return to a threshold of just a few months for building a bomb.

He rejected notions that a military option or sanctions option could alone rein in Iran’s program.

The Chairman of the Foreign Relations Committee Senator Bob Corker (R-TN) started off the hearing by railing against the deal, which he compared to an athlete being required to mail in his own urine sample to drug testers.

He told Kerry, Energy Secretary Ernest Moniz and Treasury Secretary Jack Lew that he thought they had been “fleeced” by Iran, which could get more than $100 billion in frozen assets as sanctions are lifted.

“What I think you have actually done in these negotiations is codified a perfectly aligned pathway for Iran to get a nuclear weapon just by abiding by this agreement … In the process of being fleeced, you have turned Iran from being a pariah to now Congress being a pariah,” he said.