Iran is biggest long-term security threat to the US: Heritage Foundation
Iran has the potential to develop a nuclear weapon once the deal with the US closes, making it "by far the most significant security challenge to the United States, its allies, and its interests in the greater Middle East," and a bigger risk to US security than perhaps ISIS or Al-Qaeda, warns the Heritage Foundation in a new threat assessment. This follows concerns from the Washington Institute for Near East Policy's Michael Singh, who pointed out that "while Iran's nuclear weapons capability will grow, the tools available to the United States to counter and contain it will be diminished." Iran also poses a cyber security threat and sponsors militias and terrorist groups such as Hezbollah.

An Iranian woman walking past an anti-US mural painted on the wall of the former US Embassy in Tehran. Thomson Reuters

Some security experts warn that the biggest threat to US security might not be one that gets the most attention.

Counterterrorism officials and the public are on high alert from terrorism threats, but a new threat assessment from the conservative Heritage Foundation warned that Iran "represents by far the most significant security challenge to the United States, its allies, and its interests in the greater Middle East."

Iran might not be as much of a short-term threat to US domestic security as terrorist groups like ISIS and Al Qaeda. But its potential for developing a nuclear weapon once its deal with the US expires makes it a significant long-term threat.

The deal the Obama administration struck with Iran limits the country's capacity for developing a nuclear weapon in exchange for sanctions relief, but after 10 years the Shia Islamic theocracy could start ramping up its nuclear program.

"They're very patient and they're very strategic," Michael Pregent, an adjunct fellow at the Hudson Institute and former US Army intelligence officer in Iraq who opposes the Iran deal, told Business Insider. "For us, 15 years seems like a long time, for them it doesn't … They'll be able to weaponize in 15 years. And then they'll be the dominant force in the Middle East."

A fellow for the Washington Institute for Near East Policy expressed similar concerns earlier this year.

"While Iran's nuclear weapons capability will grow, the tools available to the United States to counter and contain it will be diminished," Michael Singh, a former senior director for Middle East affairs at the National Security Council, wrote in January.

"Iran's growing nuclear activities and its remaining nuclear infrastructure will have been granted legitimacy by the international community, its defensive and offensive military capabilities will be greater, and the United States will have agreed not only to refrain from imposing additional sanctions on Iran for nuclear advances but will also have suspended its most significant sanctions."

And if the US wants to keep the deal from falling apart, the government might be reluctant to rebuke Iran for its activities outside the country.

Increasing sanctions could "kill the deal, and that's why the administration is so against enforcing anything, even UN Security Council resolutions," Pregent said.

But Iran's nuclear program isn't all we should be worried about. The country also poses a cybersecurity threat and sponsors militias and terrorist groups like Hezbollah.

And the sanctions relief that Iran got from the nuclear deal could help the country increase its terrorism operations in other countries.

"They're not changing their behavior," Pregent said. "They're more provocative. They're able to do more … They're a more destabilizing force now post-Iran deal."

Iran has been supporting Shia militias that are fighting ISIS in Iraq. While these militias are an effective fighting force against the terrorist group, Sunnis have accused them of torturing and kidnapping civilians simply for living in ISIS-held territory.

Hezbollah is also a concern. The Lebanese Shia militant group that receives funding from Iran sometimes carries out attacks on Iran's behalf.

"Given Hezbollah's close ties to Iran and its past record of executing terrorist attacks on Iran's behalf, there is a real danger that Hezbollah terrorist cells could be activated inside the United States in the event of a conflict between Iran and the US or Israel," the Heritage report noted.