Updated

The Italian island of Giglio made final preparations Sunday on the eve of an unprecedented attempt to raise the 114,500-ton Costa Concordia cruise ship from its watery grave.

Salvage workers could be seen fixing the giant metal chains and cables that will hoist up the 290-metre (951-foot) wreck, which is roughly the length of three football fields.

The civil protection agency, which is overseeing the project, gave its final go-ahead on Sunday, saying the weather forecast looked favourable.

The biggest rotation of a passenger ship ever attempted is set to begin shortly after 6:00 am (0400 GMT) on Monday and could last up to 12 hours.

"Parbuckling operations of the Costa Concordia will begin tomorrow," the agency said, using the technical term for rolling a ship upright.

Once the Costa Concordia is upright, the plan is to stabilise it, refloat it and then tow it away for scrapping in a shipyard early next year.

The head of the operation, Nick Sloane, has warned it is now or never for the Costa Concordia because the hull is gradually weakening and might not survive another winter.

The project so far has cost more than 600 million euros ($798 million) and one of the insurance companies picking up the tab estimates the bill could run to $1.1 billion (830 million euros).

The ship has been lying on its side just off Giglio ever since it hit rocks near the shore and keeled over with 4,229 people on board in January 2012.

The crash -- allegedly caused by captain Francesco Schettino ordering a risky "salute" manoeuvre near the island -- sparked a panicked night-time evacuation.

Thirty-two people lost their lives.

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.

All maritime traffic will be blocked in the area, one of Europe's biggest marine sanctuaries, until the parbuckling is completed.

The operation holds special significance for islanders whose lives were turned upside down by the tragedy, and a special prayer was said for the salvage during Sunday mass.

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.

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 have been fixed onto the side of the ship currently exposed, designed to act as brakes to prevent it from flipping over too far.

Once the rollover is completed, workers will weld more tanks or "sponsons" onto 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, probably early next year.

The salvage operation has been delayed repeatedly, mainly due to the difficulties of drilling into the granite seabed to install a metal structure to support the ship.

The project is being financed by the insurers of the ship's owner Costa Crociere, which is Europe's biggest cruise operator and part of the leading company in the sector, the US-based Carnival.

Four crew members and the head of Costa Crociere's crisis unit were handed short prison sentences earlier this year after negotiating plea bargains over their role in the crash.

Schettino -- dubbed "Captain Coward" and "Italy's most hated man" in the press -- is on trial accused of manslaughter and abandoning the liner before all its passengers had been evacuated.

Dozens of survivors are also suing Costa Crociere in civil courts and calling for more stringent international rules on cruise liners.