By Tom Gibb BBC South America correspondent

An Argentine expedition is preparing to search for the wreck of the Argentine cruiser the General Belgrano, sunk at the start of the Falklands War by a British nuclear submarine more than two decades ago.

Three hundred and twenty-three Argentines died in the attack - the single largest loss of life during the conflict.

National Geographic say they will use an unmanned submarine to try to locate the wreck in waters off the southern coast of Argentina.

The sinking of the Belgrano in May 1982 at the start of the Falklands War is still controversial.

The Argentines complain the ship was sunk outside a 320 km British imposed exclusion zone whilst heading back to port.

The British say the Belgrano posed a threat to its task force, whatever its location.

Now, National Geographic with the help of the Argentine navy will search for the wreck.

It is thought to be more than 4 km (two and a half miles) deep in notoriously rough seas, some 180 km off the Argentine coast.

The expedition will use similar equipment to that used to find the Titanic.

Memorial planned

If successful, an unmanned submarine will lay a plaque to the dead as well as record images for a television documentary.

Before being bought by Argentina, the Belgrano was a US cruiser called the Phoenix and was one of the survivors of the Japanese attack on Pearl Harbour.

Argentine veterans have welcomed the expedition to find the wreck, hoping it will show which way the hull was pointing when the ship was struck by British torpedoes.

The sinking provoked the largest single loss of life in the Falklands War, scuppering efforts to negotiate a settlement.

The sovereignty of the islands known as the Malvinas in Argentina is still in dispute between the two countries although friendly relations in other areas have been restored.