Iran is a larger problem for the United States than the threat of the Islamic State's jihadist aggression, former Secretary of State Henry Kissinger maintained in an NPR interview Saturday.

"I think a conflict with ISIS — important as it is — is more manageable than a confrontation with Iran," Kissinger told NPR's Scott Simon,  explaining that Iran is a powerful nation with incentive to reconstruct its historical ancient Persian Empire while ISIS "is a group of adventurers with a very aggressive ideology."

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"There has come into being a kind of a Shia belt from Tehran through Baghdad to Beirut," said Kissinger, secretary of state to late Presidents Richard Nixon and Gerald Ford. "This gives Iran the opportunity to reconstruct the ancient Persian Empire — this time under the Shia label — in the rebuilding of the Middle East that will inevitably have to take place when the new international borders [are] drawn. The borders of the settlement of 1919-'20 are essentially collapsing."

ISIS, in comparison, still has a way to go before it poses the threat that Iran does, said Kissinger, as "they have to conquer more and more territory before they can become a strategic, permanent reality."

The former secretary, who gives a historical perspective of world affairs and events in his new book "World Order," said ISIS does, however, present a significant threat that will need addressed.

"They have cut the throat of an American on television," said Kissinger. "This is an insult to the United States, which requires that we demonstrate that this is not an act that is free. I would strongly favor a strong attack on ISIS for a period that is related to the murder of the American."

After that, he said, the United States needs to "go into the long-range problem.

"I think when we are dealing with a unit like ISIS, we should not get into a position where they can lead us by establishing ground forces," Kissinger told NPR. "But we should set strategic objectives where we thwart any goal they set themselves, which we should be able to do by superior air power."

And if the United States can enlist other countries in its fight against ISIS, or get "other more local groups to do the ground fighting, we might actually destroy them."

Kissinger is scheduled to appear on CBS' Face the Nation Sunday.

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