Former U.S. Sen. Sam Nunn, a nuclear expert, is publicly backing the Iran nuclear deal negotiated by the United States and other world powers.

Nunn, who spent much of his Senate career working on nuclear nonproliferation and now runs the Nuclear Threat Initiative, told WABE-FM that under the agreement, “it’s going to be a lot harder for the Iranians to get a nuclear bomb over the next 10 or 15 years.”

The former Democratic senator from Georgia said the agreement is “far from a perfect document,” but he said much of the criticism it now faces, particularly from congressional Republicans, is rooted in the idea that it will not affect Iran’s behavior as a disruptive force in the Middle East through its support of groups such as Hezbollah and Hamas.

“But this negotiation was not aimed at this behavior,” Nunn said. “And these debates are getting very much mixed between those goals, because if we had aimed it for instance at Syria behavior of Iran, or Hezbollah or Hamas, we wouldn’t have had Russia participate. And we probably would not have had much enthusiasm for the oil embargo that our European allies have put on.

“So we have to parse this a little bit and say: ‘What was the agreement aimed toward? What were the negotiations aimed toward? What were the U.N. resolutions aimed toward? And what was the economic embargo — which has been very effective — aimed toward?’” Nunn said. “And it was to prevent them from getting a bomb.”

Nunn added: “When you get right down to it, what we’re doing: We’re buying time. We’re not getting an insurance policy that they’ll never have a weapon.”

Nunn said the George W. Bush administration also aimed any negotiations at halting a bomb, not Iran’s behavior in the region.

He also countered the argument that lifting sanctions will help Iran’s economy, giving it more funding to build a bomb.

“I think that’s a legitimate concern,” Nunn said. “I think that is the best argument that opponents of this agreement are making, but it has a weakness. And the weakness is you have to back up and say what is the assumption of that argument.

“And the assumption of that argument is that we can continue the embargo. And the United States can make that decision and our allies — including Russia and China — will all salute and say, ‘Yes sir, Uncle Sam, we’ll go along with that.’ And our European allies will continue to not buy oil, which has been devastating to the Iranian economy. That assumption is false.”

Congress is expected to vote on the agreement in September, after a fierce two months of lobbying.

While Republicans are lining up against the deal, President Barack Obama only needs Democrats to hold up an expected veto to allow the agreement to take effect.