In their place, hundreds of robot-run trucks and cranes shuttle among neat stacks of freight containers, making the terminal at Maasvlakte in Rotterdam one of the most automated, and seemingly secure, shipping centers in the world.

Yet security measures for port facilities and ships here and across the seven seas have lagged far behind the strict rules enforced at airports and on aircraft since the Sept. 11 attacks.

Now the United States is leading a rush to plug these holes, after the FBI and other agencies have warned that shipping is at risk.

"There is evidence that the al-Qaida terrorist grouping has taken note of the value and vulnerability of the maritime sector," said Tim Spicer, chairman of Aegis Defense Services, a British security consulting firm.

With commercial ships transporting 80 percent of the world's traded goods, security experts worry that vessels, ports and other links in the maritime economic chain might make tempting targets. A terrorist attack could sink a ship, cripple a port, panic markets and disrupt world trade.

Lloyd's of London, the insurance market, considers an attack on a cruise ship to be "a high likelihood," said Neil Smith, marine manager for the Lloyd's Market Association.

A rising trend in piracy compounds concerns. On March 26, men armed with automatic weapons boarded a chemical tanker sailing near the Strait of Malacca, the passage between Singapore and the Indonesian island of Sumatra. They dis-

abled the ship's communications equipment, practiced steering the vessel for an hour, stole some technical documents and left.

"The possibility of terrorists linking up with pirates to hijack commercial vehicles containing ... liquid natural gas or liquid petroleum gas and crashing it into a port is of great concern to Singapore" and other maritime nations, said Singapore's deputy prime minister, Tony Tan.

Security is about to tighten up in this new year.

Under U.S. pressure, the International Maritime Organization — the U.N. agency that monitors shipping safety — is requiring port facilities, stevedoring companies and owners of ships larger than 500 tons to make detailed plans for responding to a terrorist threat. This International Ship and Port Facility Security Code is the shipping industry's biggest anti-terrorist effort so far.

Europe Container Terminals, or ECT, will install an additional two miles of fencing and 15 more closed-circuit TV cameras at its Maasvlakte wharves.

The U.S. Department of Homeland Security will take a separate step this month, introducing a "smart box" program to make containers more tamperproof by encouraging shippers to use electronic sensors that show if anyone has opened a container's doors.

Still, some industry officials and security experts argue that too few companies and maritime authorities are doing enough to meet the new security code's July 1 deadline. The Panama Canal Authority, for example, has yet to hire consultants to begin assessing shortcomings at the Western Hemisphere's busiest strategic waterway.

Experts say more also needs to be done to upgrade security at ports and shipping firms in poor nations. Some 55,000 ships and 20,000 port facilities must comply with the new security directive, and 32 countries are seeking technical help from the International Maritime Organization.

"A smaller port in Central or South America — are they going to be ready in time? I don't know," said Chris Koch, president of the World Shipping Council, a ship owners' association based in Washington.

Experts have long warned that a terrorist group might try using a shipping container to smuggle a nuclear warhead or some other weapon of mass destruction into the United States or Europe. They say terrorists might also try to hijack a cruise ship or a tanker laden with oil or flammable gas, then rig it with explosives and turn it into a floating bomb.

The risk of a maritime terrorist strike isn't just hypothetical. Suicide attacks killed 17 sailors on the American destroyer USS Cole in Yemen in 2000 and a crewman on the French oil tanker Limburger off Yemen's coast in October 2002. Terrorists tried and failed to attack another U.S. destroyer before succeeding against the Cole, and authorities in Singapore and Morocco have recently foiled similar plots.

To help deter attacks on civilian ships, cruise lines now require boats and unauthorized visitors to stay at least 200 yards away from each ship when it enters a port. Passengers and crew members also need electronic identification cards to board their vessels.

Awareness of the vulnerabilities of commercial ports and shipping has intensified since Sept. 11, and the United States is the driving force.

In effect, America is pushing its border security outward. Foreign ports must now notify U.S. customs of the contents of each container heading to a U.S. port, 24 hours before the container is loaded for shipment. Under separate agreements with 18 countries, U.S. customs officers work at overseas ports to help their foreign counterparts screen the contents of U.S.-bound containers.

China, Thailand and South Africa are among the developing countries participating in this Container Security Initiative, but prospects for security improvements elsewhere in the developing world are less encouraging. Some ports and shipping firms can't afford the training and administrative changes required under the new worldwide security code.

Port officials acknowledge that a container concealing a weapon of mass destruction might pass unnoticed through a smaller port in Africa or Asia, but they argue that large ports handling containers bound for America are better equipped to detect a lethal cargo.

Since the Sept. 11 attacks, ports have also been more aggressive about refusing entry to containers they think might be dangerous. But even a well-secured port can do little to stop terrorists from hijacking a ship and sinking it in the port's main channel to paralyze traffic and trade.

"The only thing that can prevent it ... is intelligence and careful screening of all the unfamiliar vessels coming into your port," said Fer van de Laar, safety manager for the International Association of Ports and Harbors.

To inflict greater economic damage, terrorists could attack a strategic waterway such as the Suez or Panama canals, or congested shipping lanes in the straits of Malacca or Gibraltar.

By targeting the Strait of Malacca — a bottleneck for Middle Eastern oil bound for Japan — terrorists could force ships to take costlier, roundabout journeys between Asia and Europe.

Coordinated attacks on two or more maritime chokepoints could have a devastating global impact.

Yet new security measures themselves are pushing up shipping costs and slowing deliveries. ECT's expenses have risen by $9.60 or more per container as a result of steps it has taken to comply with the new security code. Jan Gelderland, the company's operations director, called the increase "really substantial" and said that the average turnaround time for a container has increased to five days from four and a half.

As new rules proliferate, even the United States is struggling to keep up.

Governments have started requiring ships to install short-range radio transponders that will let authorities track their movements close to shore. The deadline for large commercial ships is July. However, the U.S. Coast Guard needs to set up at least 250 land-based antennas and receiving stations so it can read the ships' signals.