NEW YORK - Twice, applause erupted as the owner of the rusting SS United States touted a proposal to restore the once-grand liner and set it to sea again, ferrying passengers in high-class splendor.

But no one should book their tickets just yet.

An ocean lies between the goal and the reality, including the need to marshal enormous sums of money and to decontaminate the ship of hazardous substances.

"There's a lot of homework to be done," said attorney Francis X. Nolan III, counsel to the SS United States Conservancy, which owns the ship.

Luxury line operator Crystal Cruises signed an option agreement with the conservancy that backers said on Thursday could see the ship reborn as soon as 2018, putting an end to the liner's enforced, two-decade docking in South Philadelphia.

"I'm confident," said Susan Gibbs, the conservancy executive director and granddaughter of naval architect William Francis Gibbs, who designed the ship. "I feel like the stars are aligning."

The Washington-based conservancy long sought to make the ship a floating hotel, museum, and retail venue. But when the conservancy issued a save-it-or-scrap-it deadline last fall, Los Angeles-based Crystal Cruises came forward.

The cruise line envisions the United States, once the choice of movie stars, presidents, and princes, as an 800-passenger ship where "glamour and sophistication will set the stage for the stars of today - Crystal's guests," said company CEO Edie Rodriguez. The option agreement runs for nine months, during which Crystal will conduct a feasibility study.

Making a 1952 liner both mechanically modern and compliant with current safety codes is a big and complicated undertaking. The project, if successful, is estimated to cost more than $700 million.

Last year, the entire Crystal Cruises company sold for less, purchased for $550 million by Genting Hong Kong.

And ships can be notoriously expensive to upgrade. The Queen Elizabeth 2, now docked in Dubai, its fate uncertain, cost about $90 million to build in 1969. During the next four decades, 15 times that amount was spent on refits and refurbishments, according to the British newspaper the Telegraph.

Under new ownership, Crystal has quickly expanded into river cruises, new luxury liners, and new first-class jet service. On some trips, travelers can explore the ocean in a small submarine. The SS United States could fit into that portfolio as a cool, history-comes-alive option.

"It probably can work," said David Fiorenza, who teaches economics at Villanova University.

The historic-preservation aspect of the project may attract wealthy underwriters and allow for certain tax subsidies. And, he said, the attempt to save an iconic ship is a great story, one that will generate publicity and draw supporters.

Of course, he said, attracting luxury clients requires specific targeting and advertising - it's not like throwing open the doors at Disney World. Government agencies will be watching and will require permits and approvals.

"Anytime you're dealing with water, that brings in other complications," Fiorenza said.

The concerns of the Environmental Protection Agency focus on the presence of PCBs, the cancer-causing agents often found in old paint, rubber products, and insulation.

The conservancy provided the EPA with a draft remediation plan, and the agency replied with comments on that proposal, according to EPA spokesperson Roy Seneca. No final remediation plan has been submitted by the conservancy, he said.

The conservancy envisions the ship based in New York. To move it there, the group would need the Coast Guard to issue a "dead ship tow permit," granted only after review of the plan for tugboats and lines.

The Coast Guard also could conduct an onboard inspection to ensure that the ship's seals and seams are secure, so the vessel won't sink in a navigation channel, said guard spokesperson Lt. Nick Woessner.

The United States may be "silted in," he said, meaning it could be sitting on mud, not floating on water. The Coast Guard would need to find out if that's the case, and, if so, how the conservancy plans to address it.

Generally, issuance of a tow permit can take about a month.

"We're waiting on contact from the conservancy, and more than happy to facilitate that process," Woessner said.

On Thursday, beside the Hudson River, enthusiasm around the announcement made it seem like ship already was saved. An almost theatrical production opened the news conference at Pier 88, featuring stirring martial music and nostalgic black-and-white film clips of the ship. About 100 people attended - though not everyone was impressed.

"It's conservancy puff," said Joe Henwood, head of Binnacle Group L.L.C. in Media. "It's far from over."

Henwood has promoted a plan to bring the ship to Chester and moor it near Harrah's casino as a floating hotel.

Conservancy spokesman Thomas Basile said the group met with Henwood several times, but he could provide no evidence of having investors or investment capital.

The conservancy itself operates in a constant search for money. Under the option agreement, Crystal will take over paying the $60,000-a-month cost of docking and maintaining the ship while the feasibility study goes on

The SS United States, today so forlorn, was once a heralded, trans-Atlantic liner making its way from New York to Europe. Its 1952 maiden voyage shattered the Atlantic speed record, which it still holds.

It was taken from service in 1969, and docked in Philadelphia in 1996, its interior long since stripped. Today it looms over Columbus Boulevard.

Those who sailed on the ship in its glory days have never forgotten.

Jim D'Orso, his wife, and their four children traveled aboard the United States in 1960, on the way to his Navy assignment in Germany. A friendly military-billeting agent put them in first class.

If you wanted bacon for breakfast, the retired Navy officer recalled, you didn't simply order bacon - there were five different kinds. When he asked whether his children could have baked Alaska, a vision of sculpted merengue houses and trees emerged from the kitchen.

At dinner, a string quartet played as women in gowns danced with men in tuxedos.

"Everything about the trip and the ship," said D'Orso, 85, who lives near Sacramento, Calif., "was like being in a dream."