Iranian missiles and the eastern U.S.: How big a threat?

Everyone’s been talking about the potential nuclear deal with Iran. Largely absent in the discussion, however, is the question of whether Iran could actually aim one at the United States’ homeland. During a recent gathering of potential Republican presidential candidates in in New Hampshire, Sen. Marco Rubio, R-Fla., took that issue head-on.

"Iran is developing long-range rockets that will at some point in less than a decade be capable of reaching the East Coast of the United States," Rubio said at the New Hampshire Republican Party Leadership Summit in Nashua, N.H., on April 17, 2015.

We wondered whether Rubio’s rather alarming projection was supported by publicly available evidence. We decided that we couldn’t put it to the Truth-O-Meter because it depends on intelligence we don’t have access to, and because it involves a prediction -- a type of claim PolitiFact doesn’t rate.

However, in discussions with experts, we found that the scenario Rubio laid out is plausible, if also far from a certainty. (Rubio’s staff did not return an inquiry for this story.)

To threaten the United States mainland, Iran would need a missile capable of carrying a payload of several hundred kilograms for 9,000 kilometers, according to Greg Thielmann, a former aide on the Senate Select Committee on Intelligence who is now at the Arms Control Association, who has written on the issue. (For a sense of comparison, the shortest distance for an ICBM to travel between the United States and the Soviet Union during the Cold War was 5,500 kilometers.) Thielmann calls this 9,000-kilometer threshold "a daunting technological challenge."

Officially, the Iranian government has said it is not interested in developing an ICBM. But many in the West are as skeptical of that claim as they are of Iran’s similar claim about nuclear weapons.

Indeed, Thielmann writes that Iran’s space program could easily morph into a weapons program: "Iran has outlined ambitious plans for building space launch vehicles to send satellites and astronauts into space. Iran’s space program is a proliferation concern because there is considerable overlap between developing (space launch vehicles) and ballistic missiles. The problem is further aggravated when space programs are run by the military, as is the case in Iran."

We can’t tell what’s in the minds of Iran’s leaders, of course. "They do not appear to be actively developing anything at ranges that could reach the United States, but that could change," said Matthew Bunn, an arms-control specialist at Harvard University’s Kennedy School of Government.

But let’s assume that Iran does want to build a workable ICBM. Could it do so "in less than a decade," as Rubio says? It would have a decent chance, experts say.

While Iran is still dependent on foreign suppliers for key components, "it should eventually be able to develop long-range missiles over time, including an Intercontinental Ballistic Missile or ICBM" -- the type of missile that would be needed to reach the United States, wrote Michael Elleman, a senior fellow for missile defense at the International Institute for Strategic Studies and a former United Nations weapons inspector,

"Iran’s ambitious space program provides engineers with critical experience developing powerful booster rockets and other skills that could be used in developing longer-range missiles, including ICBMs," Elleman added.

Richard Nephew, a foreign policy specialist at Columbia University, agreed that Rubio’s claim is plausible.

"Iran's ballistic missile program is advancing -- they have a rudimentary space-launch vehicle capability and, all other things being equal, they may be able to build an intercontinental capable system" within the time frame Rubio cited, Nephew said.

Several experts said the closest analogue to Iran is North Korea, though they added that the case of North Korea shows both the potential for Iran to build such a missile and the challenges it would face.

According to globalsecurity.org, North Korea may have already unveiled a KN-08 ICBM during a military parade in Pyongyang in April 2012. (Analysts aren’t certain whether it was a mock-up or a real missile.) But United States officials aren’t taking any chances with a missile that might be able to reach Alaska, 5,500 kilometers away.

Adm. William Gortney, who heads the U.S. Northern Command, said in an April 7, 2015, Pentagon briefing that "our assessment is that they have the ability to put a nuclear weapon on a KN-08 and shoot it at the homeland."

And "anything North Korea can do, Iran can do," said John Pike, the director of globalsecurity.org.

Experts, however, did caution against assuming a smooth path -- or a speedy one -- if Iran makes a serious play to build an ICBM.

For Iran, "the most obvious and unmistakable milestone would be a long-distance flight test -- not just of a booster, but also of a warhead," Thielmann said "Such an event would precede acquiring an operational capability by several years. No such event has occurred in Iran. Nor has any ICBM-sized airframe been observed, as far as we know."

If Iran wants to build an ICBM -- which, again, its leaders may or may not want to -- then the timeline seems reasonable, experts said.

Thielmann has written that some U.S. and Israeli officials have suggested an even faster timetable, one he considers implausible. He told PolitiFact that Rubio’s time frame, while still speculative, "is much more realistic" than those other assessments.

Elleman wrote that "an Iranian ICBM seems unlikely before 2020," while Anthony H. Cordesman of the Center for Strategic and International Studies offered a minimum time frame of four to 10 years.

Cordesman also noted another hurdle: Iran "would also need to have nuclear warheads to achieve any effect other than a random conventional explosion, unless it can make more progress in conventional precision-strike capability at extremely long ranges than now seems likely," Cordesman wrote.

All in all, there’s enough uncertainty about Iran’s intentions and technological capabilities to suggest that Rubio would have been better supported if he’d said "may" rather than "will." When it comes to Iran’s nuclear capabilities, there is still much uncertainty.