Waiting to guide a cargo carrier toward the Panama Canal's southern locks, Benjamin Russo gazed from his tugboat at another vessel headed north toward the Caribbean Sea.

At 650 feet long and loaded with automobiles, it was a massive ship. Yet it pales in comparison to the so-called New Panamax behemoths, up to 1,200 feet in length, which within days will begin transiting the waterway. A dress rehearsal is planned for this week when the first of the larger vessels will cross through the newly expanded locks.

Few public works projects have captured the world's imagination like the Panama Canal, which opened in 1914 and revolutionized the shipping industry by connecting the Atlantic and Pacific, short-cutting sea voyages around the tip of South America. Since passing from U.S. to Panamanian control in 1999, the canal and related economic activity have come to contribute nearly 40 percent of the Central American nation's GDP.

Already a year and a half behind schedule and eagerly anticipated, the $5.25 billion expansion is expected to double the canal's capacity, tap new markets such as liquid natural gas shipments and cut global maritime costs by an estimated $8 billion a year. Around the Western Hemisphere, ports have been making their own overhauls to receive the vessels, which are more than three football fields long, can carry about 2.5 times as many containers as those currently using the canal and are seen as the future of world shipping.

But as Panama readies for its launch party on June 26, Russo and the other 150 or so tugboat operators who work the waterway are nervous. Under the new system, they'll have to engage in tricky maneuvers in a confined space inside the locks themselves, trying to keep the bulky New Panamaxes from banging into the walls or even crushing the tugs if they lose control.

"Imagine when we're in front of the prow of those other monsters and have to tie ourselves to them," said Russo. "If something goes wrong with the tugboat and that ship keeps moving, I may not have time to get out of the way."

Under the old system, tugboats' engagement with ships has been limited to guiding them in open waterways and to the entrance of the locks, where powerful locomotives known as "mules" take over, latching on and keeping the vessels in place as the water level is raised or lowered.

There are no mules in the new setup. Instead tugs will approach a ship, latch on at both the bow and stern and accompany it inside the 1,400-foot locks. With the lock doors closed on a 1,200-foot New Panamax, there's little room to operate for the roughly 90-foot tugs positioned both fore and aft.

The shipping vessels will be running on their own propulsion throughout, and be under the control of a canal pilot who goes on board to steer. Communication between the tugs and the pilot will be key.

Experts say it's similar to locks already functioning elsewhere in the world, such as parts of the United States and Antwerp, Belgium, and that it works just fine. But with increased human involvement comes increased possibility for human error, and there will be a steep learning curve for tug operators and pilots.

"I believe there is some risk increase that's going to require a lot more training and getting used to," said Richard D. Hepburn, a retired U.S. Navy captain and author of "History of American Naval Dry Docks."

A mechanical failure such as a broken mooring or a winch or engine outage could complicate things. Panama is prone to violent storms, and analysts said there will likely be some sort of protocol for adverse weather.

"If there's a 70 mph crosswind blowing, well, you may not want to try maneuvering in until the wind abates," said Jack Leary, a marine engineer and naval architect at Leary Engineering in New Orleans.

Canal authorities say they are well equipped to deal with extreme conditions. Officials say over 60 of the 289 canal pilots and more than a third of the 150 tugboat captains have undergone simulator training. The canal became fully operational May 31 after running more than 1,000 virtual trials involving 300 possible scenarios.

Canal administrator Jorge Luis Quijano said the skills the pilots and tug operators need are being provided through a four-stage training process. Operations will ramp up slowly, with just four boats a day transiting the new locks through the end of September to allow captains to gradually gain experience.

"Bit by bit, we want to go about removing that anxiety," Quijano said.

Nevertheless, captains worry their training has not been enough as Day One of operations looms a little over two weeks after the trial.

"They can run a million simulations," said Paul Bingham, a shipping economist at EDR Group, but "you have to actually put the humans in control with all the other variables of the real world conditions of weather and lighting."

Tugboat captains are also concerned about the moment when they will approach the large ships and attach lines while still in motion. If not done properly, they say, the hydrodynamic force created by a New Panamax could sink their own boats.

"Obviously we have that fear," said Cristobal Falquez, who has been a tug captain since 1999.

Moreover, they'll have to guide the ships through 50 miles of interior waterways and often-foggy curves, including a narrow stretch nicknamed "the snake."

The captains' concerns about risks are leading to demands for better pay.

"The work has to be done," Russo said. "The thing is you have to mitigate the risks, (and) you have to remunerate for running that risk."

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Associated Press writer Juan Zamorano reported from Lago de Miraflores, Panama, and Peter Orsi from Mexico City. Kathia Martinez contributed from Panama City.

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