September 11 came from the sky in a somewhat unconventional way. Terrorists turned fully-fueled airplanes with passengers into cruise missiles, crashing them into the symbols of U.S. economic and military strength: the World Trade Center and the Pentagon.

In their desire to at least match the destructive effect of those attacks, terrorists will look for another "creative," unconventional approach.

This time, it could come from the sea.
In recent months, the issue of port security reached fever pitch over the prospect that a government-owned company of the United Arab Emirates was to manage a number of U.S. ports.

Ports oversee the annual movement of some 6 million containers, of which the U.S. Customs and Border Protection (CBP) Agency inspects perhaps 3-5 percent. Indeed, CBP has little counterterrorism intelligence to support its efforts.
In all, an estimated 7,500 foreign-flag vessels make some 51,000 U.S. port calls each year.

Yet, an attack from the sea may not necessarily come from a container offloaded from a ship.

Instead, merchant ships under terrorist control could be fashioned into floating nuclear bombs. It wouldn't take many such vessels and terrorists with state-sponsor support are assessed to have such a capability.

These terrorist ships, however, would not have to enter into a U.S. port. They only would need to come near one, thereby bypassing the much-ballyhooed "National Maritime Security Strategy" of container security.

It also would make useless Customs' Container Security Initiative program at selected foreign ports. That said, authorities still would need to expend the resources to insure against the use of containers to smuggle contraband or weapons of mass destruction.

Freighters loaded with a nuclear device could approach a significant port, such as New York City, Baltimore, Los Angeles, Houston or Seattle.

In addition, nuclear bomb-laden ships could sail up the Welland Canal with its multiple locks near Niagara or enter into the Delaware-Chesapeake Bay region. Both strategic locations provide access to major U.S. inland shipping and product distribution networks.

An Hiroshima-type bomb with an equivalent of 20,000 tons of TNT could take out a city and most people in it. The heat from the blast will evaporate most structures near the explosion and create radiation that will affect the lives of many more people.

More than 75 percent of the nation's population resides on or near U.S. coasts.

The coasts also are the location for significant U.S. infrastructure needs, such as energy and telecommunications. Some three-quarters of U.S. military assets, including bases and posts, nuclear-weapons assembly plants and nuclear reactors are near U.S. coastlines.

Merchant ships devised as nuclear bombs also could include the launching a missile from a freighter off our shores. Iran is assessed to have this capability. Such a launch would go largely undetected.

Until now, this method was regarded as an increasing threat to the United States from the sea. And it still could be.
North Korea has cooperated with Iran in developing a number of long-range missiles. It also may be assisting Iran in its nuclear weapons research. North Korea already is assessed to have between two to six nuclear devices, and counting. Like Iran, North Korea recently resumed nuclear enrichment despite worldwide condemnation.

Neither country, however, is assessed now to be able to mount a nuclear device on a missile. Yet, they could devise a chemical or biological warhead on missiles that would create serious panic upon impact.

Still, a chemical or biological warhead would not have the devastating effect of freighters as delivery vehicles for nuclear weapons. Also, detection of ships with such a nuclear device on board would be very difficult, since lead containers could shield any radiation emission.

Iran and North Korea also could insure that the nuclear bomb-laden ships are registered with the proper "flag of convenience" to avoid suspicion. There are some 130,000 merchant ships registered in 195 countries. Two of the most prominent "flag of convenience" countries are Panama and Liberia. Between them, they have more than 6,000 ships on their respective registries.

Iran and North Korea most likely would use suicide-prone terrorist groups such as al Qaeda or Hezbollah to carry out the attacks to mask their true origin. In recent months, Iran even has claimed that it has some 40,000 suicide bombers signed up to retaliate should the United States bomb its nuclear sites.
Al Qaeda also is thought to have from 15 to 50 merchant ships. Their whereabouts remain largely unknown. Hezbollah also can operate ships.

Given their high seas experience, al Qaeda and Hezbollah will know that the U.S. Navy monitors most ship communications and location before they approach U.S. waters. Such monitoring often begins at the journey's origin.

Iran or North Korea then will want to insure that any nuclear device and ship be joined at a less conspicuous intermediary country. In this way, they will seek to avoid detection while linking up with the terrorist crews.

The U.S. Navy constantly monitors ships to determine whether they are smuggling weapons and people. Yet, thousands of arms and illegal immigrants still manage to infiltrate by sea undetected into the United States each year.
This means that nuclear bomb-laden ships now could easily slip into normal merchant shipping channels without examination.

All of these elements could come together to pose a threat to the U.S. homeland that is almost unmatched by any other existing terrorist threat. Given our penchant for disastrous intelligence failures, however, I am not confident that we will detect and prevent such a holocaust in time.

F. Michael Maloof is a former senior security policy analyst in the Office of the Secretary of Defense.