BOSTON — The U.S. government is better off addressing the potential threat posed by cruise missiles and unmanned aircraft launched from near U.S. borders through law enforcement and nonproliferation measures rather than by deploying sensors and interceptors, according to a study by the Rand Corp., a federally funded think tank based in Santa Monica, Calif.

The considerable investment needed for defensive systems likely would take money away from other efforts that could better address a variety of threats, according to the report, released in early June and titled “Evaluating Novel Threats to the U.S. Homeland Unmanned Aerial Vehicles and Cruise Missiles.”

“Relative to the threat posed by [unmanned aircraft] and cruise missiles, active defense systems are too costly to operate, can defend only very small areas, and have limitations even within these small, defended areas,” the report states. “It is our conclusion that investments in defenses at the point of attack will take away resources from other more- productive defense investments focused on preventing a much wider range of attacks before they occur.”

The potential for a missile attack from a vessel operating near
shores was addressed in a National Intelligence Estimate conducted in 2001. Industry and military officials have cited short-range ballistic missiles as a possible threat, though the
report noted that the National Intelligence Estimate described cruise missiles as a more likely threat.

The likelihood of this type of attack is hard to predict, the report states, noting that the Hezbollah Islamic paramilitary group’s July 2006 cruise missile attack on an Israeli ship during fighting in
was a surprise both to Israeli and
intelligence officials.

The report said it is not surprising that potential enemies are interested in cruise missiles and unmanned aerial vehicles since the Pentagon has repeatedly demonstrated their effectiveness in combat. Such vehicles are attractive more for their ability to evade defenses and make simultaneous attacks than for their firepower, the report said.

Cruise missiles can function as a “poor man’s air force,” the report said.

However, the cost of these weapons, though considerably lower than fielding an air force, likely would drive most adversaries to seek less expensive means of attack, the report said. The
United States
has relatively porous borders and a wealth of poorly defended targets that are vulnerable to weapons far cheaper than cruise missiles, the report said.

The report described unmanned aircraft and cruise missiles as a “niche threat” and recommended that it be addressed through diplomatic and other efforts to prevent proliferation of the relevant technology, actions against groups seeking to acquire the hardware, and mitigation and recovery plans that could be implemented if such an attack does take place.

“Such an investment will increase security not only against cruise-missile and [unmanned aircraft] attacks but against a wide variety of potential terrorist attacks,” the report states.

Some spending specifically on the threat of unmanned aircraft and cruise missiles may be warranted to help
authorities identify potential sources of these weapons, assess their potency and develop post-attack recovery plans, according to the report.

The Pentagon currently has no strategy for dealing with attacks by drone aircraft or short- range missiles. Rick Lehner, a spokesman for the U.S. Missile Defense Agency, described the threat of a short-range ballistic missile fired from a vessel near the
coast as “serious.” He said that while the agency has not been directed to provide a solution, it could offer a flexible response through its mobile assets including Aegis ships equipped with sensors and interceptors, Patriot interceptors, and the Terminal High Altitude Area Defense System.

deferred to U.S. Northern Command regarding cruise missile and drone aircraft threats. U.S. Air Force Master Sgt. Anthony Hill, a spokesman for Northern Command, did not respond by press time to a request for comment.

Philip Coyle, a former top weapons tester at the Pentagon, said he agrees with the
study recommendations. The cost of lining the
coastline with interceptors to knock down short-range missiles and unmanned aircraft would be enormous, said Coyle, currently a senior advisor to the Center for Defense Information, a Washington-based think tank.

The current
struggle to halt the flow of illegal immigration from
is an indication of how difficult it is to deploy effective defensive measures, Coyle said.

Ellison, president and founder of the Arlington, Va.- based Missile Defense Advocacy Alliance, said protecting the United States from missiles and unmanned aircraft is “not an either-or” proposition. While nonproliferation, counter intelligence and law enforcement measures should be used to address the threat, it makes sense to deploy sensors and interceptors that the military has already spent billions of dollars to develop and demonstrate, he said in a June 25 e-mail.