There's no end in sight for the treasure dispute between U.S.-based deep-sea explorers and the Spanish government.

Odyssey Marine Exploration of Tampa, Fla., is battling Spain in federal court over the ownership of an estimated $500 million of coins and other artifacts. The treasure was rescued last year from what is believed to be a 19th-century Spanish shipwreck.

Attorneys for both sides told a federal magistrate judge Monday that they are still exchanging information and may be doing that well into the fall or later.

That means it will be at least next year before the case makes it to trial.

Spanish officials have said the 19th-century shipwreck at the heart of the dispute is the Nuestra Senora de las Mercedes — a Spanish warship sunk by the British navy southwest of Portugal in 1804 with more than 200 people on board.

Tampa, Fla.-based Odyssey Marine Exploration had announced in May 2007 that it had discovered the wreck, code-named "Black Swan," in the Atlantic — and its cargo of 500,000 silver coins and other artifacts worth an estimated $500 million.

At the time, Odyssey said it did not know which ship it was, and flew the treasures back to Tampa without Spain's knowledge, from an airport on the British colony of Gibraltar on Spain's southwestern tip.

The Spanish government filed evidence in a Tampa federal court to support its claim.

"We are talking about the remains of a Spanish navy vessel and the human remains of Spanish naval servicemen who died on board which have been illegally disturbed," Culture Ministry Director General Jose Jimenez said last month.

"It is the property of the Spanish navy, government and people, and we want it all back," said Adm. Teodoro de Leste Contreras, who runs a naval museum owned by the ministry.

In March 2007, Spain granted the company permission to search its waters off the Strait of Gibraltar for the HMS Sussex, which sank in a 1694 storm off the Rock while leading a British fleet into the Mediterranean Sea for war against France. The strait is the strategic waterway that connects the Atlantic and the Mediterranean.

But that permit was only for exploration, not for removing anything from the Sussex if it were found.

Odyssey denied that the wreck it found was the Sussex.

The coins — mostly silver pieces — could fetch several hundred to several thousand dollars each, with some possibly commanding much more, he said.

Value is determined by rarity, condition and the story behind them.

Experts said that controlled release of the coins into the market along with aggressive marketing should keep prices at a premium.

The richest-ever shipwreck haul was yielded by the Spanish galleon Nuestra Senora de Atocha, which sank in a hurricane off the Florida Keys in 1622. Treasure-hunting pioneer Mel Fisher found it in 1985, retrieving a reported $400 million in coins and other loot.