The Pentagon is quietly working to set up an elaborate network of defenses to protect American cities from a barrage of Russian cruise missiles.

The plan calls for buying radars that would enable National Guard F-16 fighter jets to spot and shoot down fast and low-flying missiles. Top generals want to network those radars with sensor-laden aerostat balloons hovering over U.S. cities and with coastal warships equipped with sensors and interceptor missiles of their own.

One of those generals is Adm. William Gortney, who leads U.S. Northern Command, or NORTHCOM, and North American Aerospace Defense Command, or NORAD. Earlier this year, Gortney submitted an “urgent need” request to put AESA radars on the F-16s that patrol the airspace around Washington. Such a request allows a project to circumvent the normal procurement process.

While no one will talk openly about the Pentagon’s overall cruise missile defense plans, much of which remain classified, senior military officials have provided clues in speeches, congressional hearings and other public forums over the past year. The statements reveal the Pentagon’s concern about advanced cruise missiles being developed by Russia.

“We’re devoting a good deal of attention to ensuring we’re properly configured against such an attack in the homeland, and we need to continue to do so,” Adm. Sandy Winnefeld, vice chairman of the Joint Chiefs of Staff, said during a May 19 speech at the Center for Strategic and International Studies, in Washington.

We’re devoting a good deal of attention to ensuring we’re properly configured against such an attack in the homeland, and we need to continue to do so. Adm. Sandy Winnefeld, vice chairman of the Joint Chiefs of Staff

In recent years, the Pentagon has invested heavily, with mixed results, in ballistic missile defense: preparations to shoot down long-range rockets that touch the edge of space and then fall toward targets on Earth. Experts say North Korea and Iran are the countries most likely to strike the U.S. or its allies with such missiles, although neither arsenal has missiles of sufficient range so far.

(Related: The Middle East Has Four Minutes To Act If Iran Fires a Missile)

But the effort to defend the U.S. mainland against smaller, shorter-range cruise missiles has gone largely unnoticed.

“While ballistic missile defense has now become established as a key military capability, the corresponding counters to cruise missiles have been prioritized far more slowly,” said Thomas Karako, a senior fellow at the Center for Strategic and International Studies, in Washington. “In some ways, this is understandable, in terms of the complexity of the threat, but sophisticated cruise missile technologies now out there are just not going away and we are going to have to find a way to deal with this — for the homeland, for allies and partners abroad, and for regional combatant commanders.”

Intercepting cruise missiles is far different from shooting down a missile of the ballistic variety. Launched by ships, submarines, or even trailer-mounted launchers, cruise missiles are powered throughout their entire flight. This allows them to fly close to the ground and maneuver throughout flight, making them difficult for radar to spot.

“A handful of senior military officials, including several current or past NORTHCOM commanders, have been among those quietly dinging the bell about cruise missile threats, and it’s beginning to be heard,” Karako said.

While many of the combatant commanders — the 4-star generals and admirals who command forces in various geographic regions of the world — believe cruise missiles pose a threat to the United States, they have had trouble convincing their counterparts in the military services who decide what arms to buy.

A handful of senior military officials, including several current or past NORTHCOM commanders, have been among those quietly dinging the bell about cruise missile threats, and it’s beginning to be heard Thomas Karako, missile defense analyst at CSIS

Fast-track requests like Gortney’s demand for new radars on F-16s have been used over the past decade to quickly get equipment to troops on the battlefield. Other urgent operational needs have included putting a laser seeker on a Maverick missile to strike fast-moving vehicles and to buy tens of thousands of MRAP vehicles that were rushed to Iraq to protect soldiers from roadside bomb attacks.

Last August, at a missile defense conference in Huntsville, Ala., then-NORTHCOM and NORAD commander Gen. Charles Jacoby criticized the Army and other services for failing to fund cruise missile defense projects. NORTHCOM, based in Colorado, is responsible for defending the United States from such attacks.

“I’m trying to get a service to grab hold of it … but so far we’re not having a lot of success with that,” Jacoby said when asked by an attendee about the Pentagon’s cruise missile defense plans. “I’m glad you brought that up and gave me a chance to rail against my service for not doing the cruise missile work that I need them to do."

But since then, NORTHCOM has been able to muster support in Congress and at the Pentagon for various related projects. “We’ve made a case that growing cruise missile technology in our state adversaries, like Russia and China, present a real problem for our current defenses,” Jacoby said.

One item at the center of these plans is a giant aerostat called JLENS, short for the Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System. The Pentagon is testing the system at Maryland’s Aberdeen Proving Ground, a sprawling military complex north of Baltimore. Reporters have even been invited to see the tethered airship, which hovers 10,000 feet in the air.

We’ve made a case that growing cruise missile technology in our state adversaries, like Russia and China, present a real problem for our current defenses. Gen. Charles Jacoby, former commander, NORTHCOM and NORAD

JLENS carries a powerful radar on its belly that Pentagon officials say can spot small moving objects – including cruise missiles – from Boston to Norfolk, Va., headquarters of the U.S. Navy’s Atlantic Fleet. Since it’s so high in the air, it can see farther than ground radars.

JLENS is in the early stages of a three-year test phase, but comments by senior military officials indicate the Pentagon in considering expanding this use of aerostats far beyond the military’s National Capital Region district.

“This is a big country and we probably couldn’t protect the entire place from cruise missile attack unless we want to break the bank,” Winnefeld said. “But there are important areas in this country we need to make sure are defended from that kind of attack.”

New missile interceptors could also play a role in the network too.

“We’re also looking at the changing-out of the kinds of systems that we would use to knock down any cruise missiles headed towards our nation’s capital,” Winnefeld said.

Ground-launched versions of ship- and air-launched interceptors could be installed around major cities or infrastructure, experts say. Raytheon, which makes shipborne SM-6 interceptors, announced earlier this year that it was working on a ground-launched, long-range version of the AMRAAM air-to-air missile.

The improvements make the missiles “even faster and more maneuverable,” the company said in a statement when the announcement was made at the IDEX international arms show in Abu Dhabi in February.

The Threat

Driving the concern at the Pentagon is Russia’s development of the Kh-101, an air-launched cruise missile with a reported range of more than 1,200 miles.

(Related: The US Missile System Driving a Wedge Between China, South Korea)

“The only nation that has an effective cruise missile capability is Russia,” Gortney said at a March 19 House Armed Services strategic forces subcommittee hearing.

Russian cruise missiles can also be fired from ships and submarines. Moscow has also developed containers that could potentially conceal a cruise missile on a cargo ship, meaning it wouldn’t take a large nation’s trained military to strike American shores.

The only nation that has an effective cruise missile capability is Russia. Adm. William Gortney, commander of U.S. Northern Command

“Cruise missile technology is available and it’s exportable and it’s transferrable,” Jacoby said. “So it won’t be just state actors that present that threat to us.”

During the 2003 U.S.-led invasion of Iraq, American and Kuwaiti Patriot missiles intercepted a number of Iraqi ballistic missiles, Karako said. But they missed all five cruise missiles fired, including one fired at Marine headquarters in Kuwait. In 2006, Hezbollah hit an Israeli corvette ship with an Iranian-supplied, Chinese-designed, anti-ship cruise missile, Karako said.

Shooting down the missiles themselves is a pricy proposition, which has led Pentagon officials to focus on the delivery platform.

“The best way to defeat the cruise missile threat is to shoot down the archer, or sink the archer, that's out there,” Gortney said at an April news briefing at the Pentagon.

At a congressional hearing in March, Gortney said the Pentagon needed to expand its strategy to “hit that archer.”

An existing network of radars, including the JLENS, and interceptors make defending Washington easier than the rest of the country.

“[T]he national capital region is the easier part in terms of the entire kill chain,” Maj. Gen. Timothy Ray, director of Global Power Programs in the Air Force acquisition directorate, said in March at a House Armed Services Tactical Air and Land Forces Subcommittee hearing. “We remain concerned about the coverage for the rest of the country and the rest of the F-16 fleet.”

Winnefeld said that the JLENS and “other systems we are putting in place” would “greatly enhance our early warning around the National Capital Region.”

In an exercise last year, the Pentagon used a JLENS, an F-15, and an air-to-air missile to shoot down a simulated cruise missile. In the test, the JLENS locked on to the cruise missile and passed targeting data to the F-15, which fired an AMRAAM missile. The JLENS then steered the AMRAAM into the mock cruise missile.

But there are many wild cards in the plans, experts say. While the JLENS has worked well in testing, it is not tied into the NORTHCOM’s computer network. It was also tested in Utah where there was far less commercial and civil air traffic than East Coast, some of the most congested airspace in the world. At a Senate Armed Services Committee hearing in March, Gortney acknowledged the project is “not without challenges,” but said that’s to be expected in any test program.

It is also unclear whether the JLENS over Maryland spotted a Florida mailman who flew a small gyrocopter from Gettysburg, Penn., to the U.S. Capitol lawn in Washington, an hour-long flight through some of the most restricted airspace in the country. The JLENS has been long touted by its makers as being ideal for this tracking these types of slow-moving aircraft.

Gortney, in an April 29 House Oversight and Government Reform Committee hearing about the gyrocopter, told lawmakers the JLENS “has more promise” than other aerostat-mounted radars used by the Department of Homeland Security along the border with Mexico and in South Florida. He deferred his explanation to the classified session after the public hearing.

Experts say JLENS can not just spot but track and target objects like cruise missiles, making it better than other radars used for border security.

Raytheon has built two JLENS, the one at Aberdeen and another in storage and ready for deployment.

If a cruise missile were fired toward Washington, leaders would not have much time to react.

“Solving the cruise missile problem even for Washington requires not just interceptors to be put in place, but also redundant and persistent sensors and planning for what to do, given very short response times,” Karako said