The US is building a new advanced missile defense system — and Iran could be one reason why

Iran just launched a ballistic missile in apparent violation of multiple United Nations Security Council resolutions.

On Tuesday, Reuters reportedthat Iran "tested a liquid-fueled missile ... capable of carrying a nuclear warhead" last month, citing two anonymous US officials. 

The test would mark Iran's second illicit ballistic-missile launch since the landmark nuclear deal, the Joint Comprehensive Plan of Action (JCPOA), was reached between Iran and a US-led group of six countries earlier this year.

Iran also tested a long-range, nuclear-capable Emad-class missile in October.

The July nuclear deal is aimed at implementing a number of non-binding controls on Iran's ability to stockpile fissile materials for a nuclear weapon over the next 15 years, in exchange for the lifting of most US and EU and all UN sanctions on the country. 

The deal's implementation also supersedes all previous UN Security Council resolutions related to Iran's nuclear program. So though the two missile tests are illegal under the current international framework, Iran will only be "'called upon'" to refrain from work on ballistic missiles designed to deliver nuclear weapons for up to eight years" once the JCPOA goes into effect, according to Reuters.

The ballistic tests might complicate the deal's implementation. Iran has violated UNSC resolutions and launched nuclear-capable long-range missiles — at the same time it's agreed to a series of over decade-long limitations on its nuclear program. This contradictory behavior that might suggest a split within Iran's notoriously fictionalized regime.

But the test probably won't come as much of a surprise to US officials, as there have been two major indications that the US didn't think nuclear diplomacy would be enough to arrest Iran's ballistic-missile progress.

First, the US's top missile defense official expected these kinds of tests to take place. Vice Admiral James Syring, the head of the US Missile Defense Agency, testified before congressional subcommittees on June 11, 2014, and March 19, 2015. Both times, he said he anticipated major Iranian ballistic missile advances in the near term.

Lockheed MartinA Lockheed Martin MEADS, or medium extended air defense system, in action.

In his June 2014 testimony before the Senate Appropriations Committee's defense subcommittee, Syring explicitly warned "Iran could develop and test an ICBM capable of reaching the United States by 2015."

His assessment echoed deputy defense Secretary M. Elaine Bunn's April 2, 2014, congressional testimony that Iran had the capability and intention of developing long-range, space-capable weapons systems.

"While Iran has not yet deployed an ICBM, its continued efforts on space launch vehicles, along with its desire to deter the United States and our allies, provide Iran with both the means and the motivation to develop longer-range missiles, including an ICBM," Bunn told the Senate Armed Forces Committee's subcommittee on strategic forces.

In his March 2015 testimony before the House Armed Services Committee's subcommittee on strategic forces, Syring was less specific about Iran's missile-test plans. But he laid out a picture of a country looking to expand, rather than curtail, its capabilities.

"Iran has publicly stated it intends to launch a space-launch vehicle as early as this year (2015) that could be capable of intercontinental ballistic missile ranges if configured as such," Syring said. "Iran also has steadily increased its ballistic missile force, deploying next-generation short- and medium-range ballistic missiles (SRBMs and MRBMs) with increasing accuracy and new submunition payloads."

Raheb Homavandi/ReutersA military truck carrying a missile and a picture of Iran's Supreme Leader Ayatollah Ali Khamenei is seen during a parade marking the anniversary of the Iran-Iraq war (1980-88), in Tehran September 22, 2015.

Ballistic development was also apparently integral to Iran's future military posture.

"Tehran’s overall defense strategy relies on a substantial inventory of theater ballistic missiles capable of striking targets in southeastern Europe," Syring said.

Both Syring and Bunn's assessments came well after the implementation of the interim nuclear agreement with Iran, which was reached in November 2013 and set the stage for the series of negotiations that culminated in the final landmark deal. Even during negotiations for a major arms control accord, top US missile defense officials did not expect Iran to slow its missile development.

And the US recently restarted a missile defense program that's especially well-suited to countering an emerging Iranian capability. In August, nearly a month after the JCPOA was reached, the Department of Defense awarded a $9.8 million contract to Boeingto "define a concept" for a multiple-kill vehicle or multiple-object kill vehicle (MVK). An MKV is an anti-missile system in which a single interceptor launches several projectiles that can destroy multiple incoming targets.

An MKV program was killed in 2009 shortly after the start of Barack Obama's first term as president, but reintroduced under the May 2015 National Defense Authoritarian Act.

YouTubeA December 2008 free-flight hover test of a Lockheed Martin-built Multiple Kill Vehicle (MKV-L

According to Space News, the MKV fills a gap in US missile defense capabilities. In one possible attack scenario, an adversary would launch warheads along with decoys meant to fool existing defense systems.

An MVA is supposed to be capable of destroying both the decoy and the actual warhead. It's also possible an adversary would launch multiple missile salvos specifically meant to fool US missile defense that an MKV would still be capable of intercepting.

In his March 2015 testimony, Syring touted the benefits of the MKV, claiming it would "revolutionize" US missile defense. He also identified Iran as one country pursuing the kinds of capabilities that the MKV is almost purpose-built to counter.

"Iran ... has publicly demonstrated the ability to launch simultaneous salvos of multiple rockets and missiles," Syring said.

According to Space News, the Pentagon aims for the MKV to go online by 2020. Assuming the JCPOA is implemented next year, the nuclear deal's nonbinding limits on Iran's ballistic missile program will be lifted in 2024.