The controversial July 18 accord on Iran's nuclear programs (JCPOA) is like the mythical half-full cup of water: Its supporters laud the full half while its critics lament the empty half.

One of the most significant criticisms on JCPOA is the apparent absence of any limitation on Iran's potential nuclear delivery systems, most notably on its ballistic missile. Not so, say the supporters: The JCPOA's provisions continue to restrict Iran from building "missiles designed to be capable of carrying nuclear warheads" for the next eight years, thereby significantly reducing their threat.

This is contested by none other than Iran's foreign minister, who maintains that the JCPOA has nothing to do with Iran's missiles, because they are not designed to carry nuclear weapons.

So who is right here? Will the nuclear deal with Iran reduce its missile threat, or will it leave Iran free to build nuclear-capable missiles to its heart's contents?

Like many other things in diplomacy, language is the key to this puzzle. Some ballistic missiles, such as the US Minuteman or the Russian Topol M, were built specifically for nuclear delivery. Operationally, they are "missiles designed to carry nuclear weapons." Technically, however, there is nothing to prevent them from delivering conventional warheads if needed; in other words, they are "conventional capable."

Similarly, many ballistic missiles that have been mainly built for conventional missions, such as the ex-Soviet Scud, are capable of carrying a nuclear warhead. (The Scud could carry three types of nuclear bombs). In other words, they are "nuclear capable."

Thus, the JCPOA limitation on "missiles designed to be capable of carrying nuclear warheads" can be interpreted in contradictory ways. For the supporters of JCPOA it means continued limitation on Iran's "nuclear-capable missiles." For Iran it means a limitation on missiles designed only for nuclear delivery — hence irrelevant, because all of Iran's medium-range missiles are dual purpose.

What counts is not what JCPOA proponents say but what Iran does, so it stands to reason that the nuclear deal is not going to block or even slow down any of Iran's missile programs. If anything, the money released by the JCPOA is bound to accelerate them.

But are the Iranians really after long-range missilery? Some advocates of the deal believe that under Iran's current president the focus has shifted from long-range to short-range systems. To substantiate this claim, they argue that Iran has not tested any medium-range missile for three years. This, however, is incorrect: The Iranians publicly announced their latest medium-range Shahab 3 test on January 2014, less than two years ago. The hiatus since then may well reflect not the absence of flight tests but a policy of concealment.

Indeed, the preceding flight tests in 2011 were concealed by Iran until unnamed countries leaked their existence to the UN. Incidentally, those were the longest range ever and the first ones that were fired into the Indian Ocean. And while no medium-range ballistic missile test was announced by Iran in the last year, it rolled out a 2,000+ kilometer range cruise missile just six month ago, potentially an even greater threat than equivalent range ballistic missiles.

Not to worry, claim the nuclear deal advocates: Iran's conventional missiles are inaccurate, hence they are neither game changers nor existential threats. Again, this is more wishful thinking than the truth.

Iran is introducing high-precision capabilities to its entire gamut of ballistic weapons, from its tactical rockets all the way to its medium-range Shahabs. Anthony Cordesman predicted in his October 2014 report that by 2016 Iran will deploy a 1,700-kilometer-range precise, terminally guided variant of the Shahab 3. Right on cue, a flight test of a terminally guided version of the Shahab 3 appeared in a recent Iranian video clip from Sept. 27, 2015.

As for the gulf region, shorter-range precision missiles that can hit individual aircraft shelters in Air Force bases are already deployed by Iran. Such precision missiles are significant game changers: They provide their operators with the attributes of modern air power but without risking pilots and expensive aircraft, a veritable revolution in military affairs.

But they are "conventional," hence relatively harmless, argue the nuclear deal proponents. This is World War II-era thinking. A precision-guided missile that can hit and destroy aircraft shelters from 1,500 kilometers can also hit and destroy critical national infrastructure such as power stations and desalination plants. It can also hit and destroy nuclear power stations, causing Chernobyl scale disaster. This is an existential threat by any other name.

Iran's missile threat is there, and it is fast growing in quantity and quality. The end of the sanctions regime is bound to accelerate it not only because of the released funds, but also because Iran's ability to draw on the latest Western technology, hitherto restricted by the need for covert acquisition channels, will now be facilitated by over-the-counter sales to the now-rehabilitated Islamic Republic of Iran.

Rubin is president of the Rubincon consulting firm and founder of Israel's Missile Defense Organization.

More In Commentary