The HMS Sussex was leading a British fleet into the Mediterranean Sea for a war against France and its leader, Louis XIV, the Sun King, when it sank in a severe storm in 1694 with 500 men and 80 guns aboard.
Historians believe the 157-foot warship was carrying nine tons of gold coins aimed at buying the loyalty of the Duke of Savoy, a potential ally in southeastern France.
If the wreckage that was found half a mile underwater off Gibraltar is the Sussex, the robot could place a very valuable booty into baskets for lifting to the surface.
King William III had authorized "a million of money" in coins which now could be worth anywhere from $500 million to $4 billion, officials said.
Such a find could also pioneer a new way of recovering sunken warships and their archaeological treasures around the world by creating alliances between governments and private companies.
Under international law, such vessels remain the property of the government that controlled them while in operation, no matter where they are found or by whom.
But governments often lack the money or experience to conduct such searches themselves, leaving treasures vulnerable to scavengers who could pillage in secrecy and sell on the black market.
The search for the Sussex is the first time a government has made a deal with a private company for the archaeological excavation of a sovereign warship.
The public-private Sussex recovery deal - reached earlier this year by the British government and a U.S.-based company, Odyssey Marine Exploration - has been criticized by some experts in Britain as setting a bad precedent for the search for archaeological treasures.
Spain also has said that Odyssey and the British government should seek its permission to continue the search, if the wreckage - whose exact location has not been disclosed - is in its territorial waters, defined as within 12 miles of its shores.
"If it is in Spanish waters, they will have to reach an agreement with the Spanish authorities to set the terms in accordance with international law and Spanish rule on the recovery of old ships," a Spanish Foreign Ministry official told The Associated Press.
Greg Stemm, Odyssey's director of operations in Tampa, Fla., and Lt. Cmdr. Richard Whalley of Britain's Ministry of Defense, who is overseeing the search operation for the British government, said they had not received such a warning from Spain's government.
"We believe the wreck is in international waters," said Whalley.
Stemm said that Spanish permission would be sought for any work in Spanish waters.
Stemm acknowledged that the partially buried wreckage that Odyssey crews found off Gibraltar after searching the region in four expeditions since 1998 may not be HMS Sussex, though he says the evidence gathered so far - including part of a cannon - suggests that it is.
George Lambrick, director of the Council for British Archaeology, has said archaeological issues will not remain a top priority under the public-private deal, derided as a for-profit salvage operation.
Stemm, whose company has long experience in deep-water recoveries, disagrees.
"This operation is being done under the most stringent archaeological requirements set by the British government after months of review," Stemm said in London, where he met Wednesday with Ministry of Defense officials.
If gold coins are recovered, Odyssey will get 80 percent of the proceeds up to $45 million, 50 percent from $45 million to $500 million, and 40 percent above $500 million. The British government gets the rest.
However, the government could keep the entire collection of artifacts intact by paying Odyssey a percentage of its appraised value.
"It's already been expensive for Odyssey in terms of the preliminary searches and research," said Whalley. Stemm estimated the search alone will cost his company more than $4 million.
Stemm said the next phase of the operation should begin later this summer, but he declined to be more specific.
By Thomas Wagner