Secretary of State John Kerry John Forbes KerryThe Memo: Warning signs flash for Trump on debates Divided country, divided church TV ads favored Biden 2-1 in past month MORE says he told Iranian officials during the nuclear talks that "death to America" chants at public rallies in their country were "pretty stupid."

"I told them that their chants of 'death to America' and so forth are not helpful, and they're pretty stupid," Kerry said, lowering his voice, during a question-and-answer session at the Council on Foreign Relations in Washington, where he sought to sell the controversial nuclear deal.

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Critics have long seized on the chants, saying it shows Tehran is hostile to the United States and that the international community should not trust negotiations with them.

Iran's Supreme Leader Ayatollah Ali Khamenei in a speech last weekend called the U.S. "arrogant" days after a nuclear accord was announced. His speech was accompanied by "death to America" and "death to Israel" chants by the crowd.

Kerry had called Khamenei's remarks vowing to defy U.S. policies in the Middle East despite the deal "very disturbing" if they represented Iran's policy.

Kerry, who led the U.S. team negotiating the Iran deal over the past two years, said Friday that he had also asked Iranian officials to no longer call for the destruction of Israel.

The Obama administration is working to sell the deal reached between the U.S., France, Britain, Germany, Russia and China with Iran to a deeply skeptical Congress and American public.

The deal lifts economic sanctions in exchange for restrictions on Iran's nuclear program.

Kerry highlighted elements of the deal he said would help prevent Iran from obtaining nuclear weapons during his Friday event.

He also downplayed the likelihood that Iran's neighbors would work to get their own nuclear weapons.

"Well first of all, you can't just go out and buy a nuclear weapon. You don't ship them FedEx," Kerry quipped. "That's just not how it works."