In 1986, Congress passed a protective law known as the R.M.S. Titanic Memorial Act, but officials at the ocean agency and elsewhere agree that it has no teeth. In 2004, the United States, France, Canada and Britain signed a draft treaty for better safeguards. But it has never been approved because it requires legislative support — which the Kerry bill would provide.

While seeking to enhance their custodial role, federal officials are now pressing the question of the missing dead. After the Titanic sank, searchers recovered 340 bodies. Thus, of the roughly 1,500 people killed in the disaster, about 1,160 bodies remain lost.

In an interview, Dr. Delgado of the ocean agency said the muddy seabed showed “clear signs” of human imprint. “Yes, you don’t see much in the way of bone,” he said, referring to the newly released photograph. “But this is clearly where someone came to rest on the bottom. It speaks powerfully to it being a grave site.”

Paul H. Nargeolet, a French mini-sub pilot who has visited the Titanic 30 times — the second-most experienced diver, after Mr. Cameron — said he had never seen any human remains.

Skeptics say that federal officials are exaggerating scanty evidence in an effort to expand their powers.

“It’s a legal tactic,” said David G. Concannon, a maritime lawyer who has dived to the Titanic’s resting place and advised the Explorers Club. “The opponents of salvage want to equate it to a grave site.”

But Mr. Delgado of NOAA defended his agency, saying: “We’re not pushing for bureaucratic turf. We’re pushing for international cooperation to protect the wreck.”