Final preparations have been made for an unprecedented attempt to raise the 114,500-ton (103,872-tonne) Costa Concordia cruise ship from its watery grave off the tiny Italian island of Giglio.
Salvage workers could be seen fixing the giant metal chains and cables that will hoist up the 290-metre wreck, which is roughly the length of three football fields.
The head of the operation, Nick Sloane, has said it is now or never for the Costa Concordia because the hull is gradually weakening and might not survive another winter.
The biggest rotation of a passenger ship ever attempted is due to begin at 6.00am (1400 AEST) on Monday, with a formal go-ahead based on the weather forecast expected later on Sunday.
The project so far has cost more than 600 million euros ($A868.18 million) and one of the insurance companies picking up the tab estimates the bill could eventually run to $US1.1 billion ($A1.19 billion).
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Once the Costa Concordia is upright, the plan is to stabilise it and then tow it away for scrapping early next year.
The ship has been lying on its side just off Giglio ever since it hit rocks near the shore and keeled over with 4229 people from 70 countries on board in January 2012.
The crash - allegedly caused by captain Francesco Schettino's bravado - sparked a panicked night-time evacuation.
Thirty-two people lost their lives in the disaster.
Using giant cement sacks and a custom-made metal platform, salvagers have so far secured the rusting hulk, which was threatening to slip from its resting place into deeper waters.
The plan is to drag it up using cables and pulleys - a complex operation that environmentalists warn could spill thousands of tons of toxic waste into the pristine waters.
The hull could bend as it is being hoisted, but the civil protection agency, which is overseeing the salvage, has ruled out the possibility of the ship splitting in two.
The operation is expected to take between 10 and 12 hours and all maritime traffic will be blocked in the area, one of Europe's biggest marine sanctuaries, until it is over.
The operation holds special significance for islanders whose lives were turned upside-down by the tragedy and there was a special prayer for the salvage during Sunday mass.
Sloane, the South African who will be at the controls, said the ship will initially be dragged up for four or five hours before gravity takes over and it begins to right itself on its own.
Giant metal tanks the size of 11-storey buildings that have been fixed on the side currently exposed are planned to act as brakes to prevent it from flipping over too far.
The island's economy depends hugely on tourism and locals say the presence of the wreck and the massive salvage operation involving 500 workers has discouraged summer visitors.
Once the roll-over - known as a "parbuckling" - is completed, workers will weld more tanks or "sponsons" on to the side of the ship that is currently under water.
These will act as giant flotation devices to allow the vessel to be towed away to be dismantled.
The salvage operation has been delayed repeatedly, mainly because of difficulties of drilling into the granite seabed to install a metal structure to support the ship.
The project is being financed by insurance for ship owner Costa Crociere, Europe's biggest cruise operator.
Four crew members and the head of Costa Crociere's crisis unit were handed short prison sentences after negotiating plea bargains over their role in the crash.
The ship's captain, Schettino, is currently on trial accused of manslaughter and abandoning the luxury liner before all its passengers had been evacuated.
