WASHINGTON – The ship in which Captain James Cook claimed Australia for the British crown is resting at the bottom of an American harbor, archaeologists said yesterday.

The Endeavour ended her days as part of the British war effort against rebellious American colonists in Newport, R.I.

Marine archaeologists say the ship was renamed the Lord Sandwich and pressed into service during the successful defense of the town against the French in 1778. Endeavour was one of 13 vessels scuttled in the harbor entrance to keep the French at bay.

“The Lord Sandwich was the Endeavour and she was in the fleet of 13,” the project director, Kathy Abbass, said after research at the Public Record Office in Kew.

Coincidentally, another of Cook’s famed vessels, the Resolution, also sank in Newport a few years after the Endeavour. That vessel’s remains are now resting under an apartment building. But the Endeavour is still under water, about 300 feet from the shoreline and about 20 feet below the surface.

Mrs. Abbass said researchers used a mixture of documentary and high-tech research, including sonar, to find six of the ships.

Further work is expected to uncover the seven other sunken ships. Excavation will begin so that the Endeavour can be identified and explored. Mrs. Abbass said the upper parts of the ships had rotted away, but the keels were preserved in the silt of the harbor.

“What we have is ballast piles pinning down the remains of the vessels,” she said. “We could find textiles, leather, and wood from the bottom of the ship.”

The archaeologists said excavation would be a slow and expensive process because the risk of damaging the ship’s fragile remains was high.

Endeavour, a 105-foot converted collier, was chosen by Cook for his first circumnavigation of the world in 1768 and taken into the Royal Navy. Proud of his first command and her robust sailing qualities, the young Lieutenant Cook remarked that “no sea can hurt her.” The barque proved to be tough, eventually becoming the first British vessel to reach New Zealand in 1769 and Australia in 1770, but by 1776 the Admiralty had no further use for the 370-ton vessel and she was sold back into merchant service.

As the Lord Sandwich, the ship was used to transport Hessian mercenaries to America at the start of the Revolution. It was later converted to a prison ship and used to hold prominent American rebels.

By 1778, as the Americans and their French allies planned to attack Newport, its British defenders began to fear that the deep-water channel nearby provided the French navy with a means to bombard the town, so the mass scuttling followed.

About 15 years later Resolution, renamed La Liberte, limped into Newport harbor in dire condition. Unable to sail, she fell into ever greater disrepair and eventually sank. Hearing of the Cook connection, many local people chipped off pieces of wood and even the sternpost as relics. Many were mistakenly sold as having come from the Endeavour.

The interest of enthusiastic souvenir seekers has continued through the centuries. A few years ago, amateur divers began to explore the wrecks and did serious harm to some of the wooden remains.