Italy's Costa Concordia cruise ship is being readied for its final voyage to the scrapyard on Tuesday, two and a half years after it crashed into an idyllic Mediterranean island in a disaster that claimed 32 lives.

A luxury liner the length of three football fields, the Costa Concordia was dragged upright in September after keeling over on its side, and is being refloated using air tanks attached to its sides like giant armbands.

The four-day journey to the port of Genoa for the 290-metre (951-foot) vessel -- roughly twice the size of the Titanic -- will be the last step in the biggest salvage operation of a passenger ship ever carried out.

"This is the finish line that all our citizens, Italians and the world, have been waiting for. Let's keep our fingers crossed," said Sergio Ortelli, the mayor of Giglio Island, a fishing community of just 1,500 residents that has been overrun by hundreds of salvage workers since 2012.

The ship will be dragged at a speed of just two knots (3.7 kilometres, 2.3 miles) per hour by two tug boats -- a Dutch vessel and a Vanuatu-flagged one -- and 12 other vessels will make up the convoy accompanying the giant ship.

The towing will begin after the arrival of a ferry from the mainland at 0630 GMT and engineers said it would take up to six hours to drag the 114,500-tonne ship into position.

Greenpeace has said it will follow the operation closely because of concern that the ship could spill toxic waste into the sea, although officials have pointed out that the environmental impact has been relatively minimal so far.

A 12-person team of salvage workers will be on the Costa Concordia itself during the journey and an evacuation plan is in place for them in case of an accident.

South African salvage master Nick Sloane said this was the "biggest challenge" of a career that has taken him to accidents at sea in six continents and two warzones.

The ship has been raised by six metres so far since the refloating operation began on July 14 and salvage engineers said they were aiming to float it by a further four to tow it through the Corsica Channel and on to northwest Italy.

- 'Remember the victims' -

The Costa Concordia struck a group of rocks just off the Tuscan island on the night of January 13 with 4,229 people from 70 countries on board, just as passengers were settling down for supper on the first day of their cruise.

The impact tore a massive gash in its hull and the ship veered sharply as the water poured in, eventually keeling over and sparking a panicky evacuation that was delayed by more than an hour in as-yet unexplained circumstances.

Its captain Francesco Schettino is on trial for manslaughter, causing a shipwreck and abandoning the ship before all the passengers had been evacuated -- even though he has claimed that he fell into a lifeboat.

Four other crew members and an executive from the ship's owner Costa Crociere, the biggest cruise operator in Europe and part of the US giant Carnival, have already plea-bargained and been convicted on lesser charges.

The cost of the entire salvage operation including the scrapping is estimated at 1.5 billion euros ($2.0 billion).

The salvage work has been a source of year-round revenue for Giglio, but many islanders complain the eyesore has hit visitor numbers over three summer seasons.

"This is something that the people of Giglio want to forget but cannot. They will always have to carry the memory of this event," Ortelli said, adding: "I don't think we should remember the ship, we should remember the victims."