Conducting an underground nuclear test is one thing, but “weaponizing” that test platform, that is, engineering it to fit in a missile nosecone and preparing it to withstand the extreme temperatures and pressures of long-distance flight is another thing altogether.

It gets worse.

There’s a good chance that Pyongyang is prioritizing the development of a warhead for its intercontinental ballistic missile (ICBM) program, which is developing a platform capable of reaching the United States.    

This notion is buttressed by North Korea’s successful satellite launch in December. For the first time since its initial attempt in 1998, Pyongyang was able to send a small satellite into orbit, using a multi-stage space launch vehicle.

Of course, the dirty little scientific secret is that if you can launch a satellite payload of, perhaps, as little as 1,000 pounds into orbit, you can also, in theory, launch a nuclear warhead toward a target anywhere on the Earth’s surface. 

Without doubt, we’re at the top of North Korea’s target list.

Halfway around the world, the news from Iran isn’t any better, where Tehran is reportedly vastly increasing its capacity for enriching uranium.

As most are aware, Tehran has been involved in a concerning — and largely covert-- nuclear program for over two decades; many international experts are convinced it has a “military dimension,” a euphemistic phrase that means Iran is building bombs. 

Naturally, Iran claims that its nuclear program is for peaceful power purposes, but that idea is undermined by the fact that Tehran has built a number of its nuclear facilities underground or on military bases. 

Indeed, the cautious-to-condemn International Atomic Energy Agency, the UN’s nuclear watchdog, has expressed worry Iran is not only being less than forthcoming about its nuclear activities (as required by international treaty), but may be involved in nuclear warhead design and associated explosives testing.

While estimates vary due to the opacity of Tehran’s nuclear activities, it’s estimated that Iran could have the scientific and material wherewithal to produce its first nuclear weapon in the next few years.

That’s not the end of it.

Like North Korea, Iran has taken a strong interest in the prestige and power associated with developing and fielding a significant ballistic missile arsenal.  Indeed due to technology transfers, some of Tehran’s missiles are based on Pyongyang’s designs.

Today, Iran has the largest and most varied ballistic missile force in the Middle East. Its missile arsenal can reportedly strike targets in the region as well as parts of Southeastern Europe — for the moment at least.

Not surprisingly, Tehran has also become involved in a civilian space program, which recently featured the Iranian press heralding the sending of a monkey into space, putting Iran on a trajectory to put a man into orbit someday. 

More importantly, again like North Korea, Tehran has developed the capability to launch a satellite into orbit — and has done so three times now, joining the club of space-faring nations.

Consequently, supported by its various space launch efforts, the U.S. intelligence community estimates publicly that Iran will be able to field an ICBM by 2015, a few short years from now.

With the right outside assistance, an ICBM capability could be here even sooner.

Of course, the question is: What can or should be done?

Diplomacy and economic sanctions haven’t worked to end North Korean or Iranian missile or nuclear programs so far. Military responses are fraught with the obvious risks and Cold War-style “Duck and Cover!” isn’t the answer, either.

While other options are being pursued to capture the growing ballistic missile and nuclear threats radiating from Pyongyang and Tehran, nothing makes more sense than investing in American missile defense.

With the technologies available today, a capable missile defense will not only protect us from ballistic missiles and their nuclear and other payloads, it will provide decision-makers with additional policy options beyond retaliation.

Perhaps even better, due to missile defense’s ability to blunt the effectiveness of the missile threat, it may well deter aggression with these weapons against us in the first place.  

As such, the best option now is to move forward vigorously with developing and deploying missile defenses such as advanced SM-3 systems to guard the homeland, our troops abroad and our allies and friends from the growing nuclear and missile menace.

Brookes is a former deputy assistant Secretary of Defense.