Engineers test tension lines on the sunken Costa Concordia cruise ship off the Italian coast as they prepare to begin salvage operations tomorrow.

The cost of the operation, which a senior official from the ship's owner Costa Cruises this week estimated at 600 million euros "and rising", is already expected to be greater than the value of the vessel itself.

The sheer scale of the Costa Concordia, a vast floating hotel which was carrying more than 4,000 passengers and crew when it went down, make the recovery one of the most complex ever attempted.

Lying on its side atop two reefs just outside Giglio harbour mouth, the 114,500 tonne vessel is the length of three soccer pitches and appears almost as big as the tiny Tuscan port where it was holed and sunk with the loss of 32 lives on January 13 last year.

A multinational team of 500 salvage engineers has occupied the island for most of the past year, stabilizing the hulk and preparing for the start of the lifting work, which is expected to early tomorrow.