Billions of dollars in gold and silver from an 18th century shipwreck have left Spain and former colony Colombia at odds over who rightfully owns the loot.

Key points: Colombia, Spain at odds over loot from the San Jose galleon

Colombia, Spain at odds over loot from the San Jose galleon The Spanish treasure ship, which sank in June 1708, was found by experts in November

The Spanish treasure ship, which sank in June 1708, was found by experts in November The ship was carrying gold, silver, gems and jewellery worth an estimated $3 billion

The ship was carrying gold, silver, gems and jewellery worth an estimated $3 billion Spanish foreign minister hoping for 'roadmap of understanding'

The disagreement is over the San Jose, a treasure ship wreck that Colombia located recently off the coast of Cartagena de Indias, its old Caribbean port city.

The ship sank in June 1708 near the Islas del Rosario, during combat with British ships attempting to take its cargo during the War of Spanish Succession.

The Spanish galleon was the main ship in a treasure fleet carrying gold and silver — likely extracted from Spanish colonial mines in Peru and Bolivia — and other valuables to King Philip V.

Colombia's president Juan Manuel Santos announced in early December that experts had found the San Jose on November 27 in a place never searched before.

So who owns the estimated $3 billion in loot?

"There are discrepancies on the issue of legal ownership," said Spain's foreign minister Jose Manuel Garcia-Margallo.

He met on Saturday with his Colombian counterpart María Ángela Holguín in Cartagena.

Spain in part has based its arguments on UN Law of the Sea rules.

But Colombia is not a signatory to the treaty, and as such not subject to those regulations.

Spain hoping for 'roadmap of understanding'

The San Jose was sunk in June 1708 off Colombia's Caribbean coast. ( National Maritime Museum/Samuel Scott )

The Spanish diplomat said that he was hoping a "roadmap for an understanding" could be hammered out given the countries' excellent relations.

What is the value of San Jose's cargo? The managing director of Sea Search Armada, Jack Harbeston, wrote an account titled The Sinking of the San Jose in 2011 where he tried to put a value on its cargo. Here is an extract: In the armada of 1708, the value of the cargo on the flagship alone exceeded Spain's annual national income from all sources. When the bullion and coins on all the galleons of the armada were totalled, it was two or three times Spain's annual income. The financial value of the shipment of 1708 is difficult to comprehend in today's (2011) terms. Given the relative buying power of silver in those days, which was far greater than it is today, the shipment would have exceeded $US50 billion. If the treasure were recovered and sold today, even allowing for the vastly reduced price of silver in recent years, it would still bring about $US2 billion, allowing for numismatic value of the silver coins, and some less significant multiplier for the stamped silver ingots. The items of greatest value on the San Jose were the gold bullion and coins. The 8 escudo coins in pristine condition would be valued in a range of $US5,000 to $10,000 each today. Other cargo of great value included jewellery, gem stones and church property. The galleons were lumbering bank vaults.

"This is not going to become an issue that divides us," Ms Holguin stressed, while acknowledging legal disagreements remained.

Only a handful of the ship's crew of 600 survived when the San Jose sank.

Treasure hunters had searched for the ship, described by some as the holy grail of wrecks, for decades.

A team of Colombian and foreign researchers, including a veteran of the group that discovered the wreck of the Titanic in 1985, studied winds and currents of the Caribbean 307 years ago and delved into colonial archives in Spain and Colombia searching for clues.

The loot's value has dropped significantly due to the falling price of silver, according to US-based company Sea Search Armada (SSA).

SSA, whose subsidiary claimed in the early 1980s that it had found the galleon's final resting place, was engaged in a long-running battle with the Colombian government.

The find was not confirmed and a US court ultimately ruled it was Colombian property.

Colombia, not surprisingly, agreed.

AFP