Spain says Odyssey Explorer took a piece of the country's heritage
The Spanish government has demanded that treasure salvaged from a shipwreck in the North Atlantic be handed over, claiming the sunken ship was Spanish.
Some 17 tonnes of gold and silver coins, worth $500m (£255m), was salvaged in May 2007 by a US firm.
Spain is suing the Florida-based Odyssey Marine Exploration, saying it is the rightful owner of the treasure.
A lawyer for the country said there was "multiple evidence" that the vessel was a famous 19th-Century Spanish galleon.
The sinking of the Nuestra Senora de la Mercedes by a British warship in 1804, off the Algarve, led the country to declare war on Britain and re-enter the Napoleonic Wars.
"The sinking of Mercedes was a pivotal event in Spanish and European history, and the site and its contents are the inalienable historical heritage and patrimony of Spain," the government said in documents filed with a Florida court on Thursday.
Odyssey Marine Exploration has kept the exact location of the site, nicknamed Black Swan, secret but says that it lies in international - not Spanish - waters.
But the Spanish government's lawyer, James Goold, said this was "irrelevant" because the ship is clearly a Spanish galleon.
In an interview with Reuters, the head of the treasure-hunting firm, Greg Stemm, said he hoped he could reach a "collaborative solution" to the long-running dispute with Spain.
He said however that even if the wreckage was identified as the Nuestra Senora de la Mercedes, Spain would have to prove both ownership and that it did not abandon it.
"That is up to the judge to determine, and it is the belief of our lawyers that Odyssey should still receive a generous salvage award," Mr Stemm said.