Mr. Netanyahu has been working to blur the distinction between Iran and the Islamic State for months, as he fights a rear-guard action against the efforts of six world powers to strike a deal to permit Iran to use nuclear energy but block its path to nuclear weapons. In his address to Congress in March, Mr. Netanyahu depicted the militant group, also known as ISIS, and Iran as rivals with similar aims despite their sectarian differences:

Iran and ISIS are competing for the crown of militant Islam. One calls itself the Islamic Republic. The other calls itself the Islamic State. Both want to impose a militant Islamic empire first on the region and then on the entire world. They just disagree among themselves who will be the ruler of that empire.

He made the same point again on Tuesday, telling reporters: “No one would dream of allowing the Islamic State of ISIS to have nuclear weapons. Why would anyone consider giving the Islamic State of Iran — which is a lot more powerful than ISIS and acts with much greater power than ISIS — to have additional power of nuclear weapons?”