"It would be an enormous mistake, a huge mistake with grave consequences for Israel and for the region, and I don’t think it’s necessary," Kerry said in an interview with NBC’s Today Show.
Israel has been a staunch opponent of the Joint Comprehensive Plan of Action (JCPOA), reached on July 14 after months of negotiations between Iran and six world powers. The agreement eases international sanctions against Iran in return for the country scaling back its nuclear program and ensuring its peaceful nature.
Israeli Prime Minister Benjamin Netanyahu, who has termed the nuclear accord a "historic mistake," spoke on Thursday of hope for another agreement "on better terms."
The Republican Party-controlled US Congress, which, like Israel, fiercely opposes any agreement with Iran over its nuclear program, is set to vote on the deal in September.
US President Barack Obama can veto the bill in the event it is rejected, which in turn can be overridden by a two-thirds majority in Congress.
