PEARL HARBOR, Hawaii - Veterans from Pearl Harbor observed Wednesday's 70th anniversary of the attack with a solemn ceremony at the site of the Japanese aerial bombing, as an aging and dwindling group of survivors announced it would disband at the end of the month.

"It was time. Some of the requirements became a burden," William Muehleib, president of the Pearl Harbors Survivors Association, said after the ceremony.

He also cited poor health among the group's 2,700 members, adding that most of the survivors have realized there are other things they'd like to do at their age.

Survivors of the Dec. 7, 1941, attack will be able to attend future commemoration ceremonies on their own. About 3,000 people, including Navy Secretary Ray Mabus and military leaders, joined this year's commemoration at a site overlooking the sunken USS Arizona and the white memorial that straddles the battleship.

Muehleib said there were 7,000 to 8,000 Pearl Harbor survivors. Local chapters of the group will function as long as they have members, and survivors can gather socially, but they will no longer have a formal, national organization.

The group's announcement came as President Obama hailed veterans of the bombing in a statement proclaiming Wednesday as National Pearl Harbor Remembrance Day. The attack, which killed 2,390 Americans, brought the United States into World War II.

"Their tenacity helped define the Greatest Generation and their valor fortified all who served during World War II," Obama said. "As a nation, we look to December 7, 1941, to draw strength from the example set by these patriots and to honor all who have sacrificed for our freedoms."

Also this week, five ash-scattering and interment ceremonies were being held for five survivors whose cremated remains were returning to Pearl Harbor after their more recent deaths.

On Tuesday, an urn containing the ashes of Lee Soucy, who died last year at 90, was placed on his battleship, the USS Utah, which lies on its side near where it sank.

Most of the 12 U.S. ships that sank or were beached that day were removed from the harbor, their metal hulls repaired and returned to service or salvaged for scrap. Just the Utah and the USS Arizona still lie in the dark-blue waters.

An urn carrying the ashes of Vernon Olsen, who was among the 334 on the Arizona to survive the attack, will be interred in a gun turret on the ship Wednesday. He died in April at age 91. Most of the battleship's 1,177 sailors and Marines who died on Dec. 7, 1941, are still entombed on the ship.

Five months after Pearl Harbor, Olsen was on the USS Lexington aircraft carrier when it sank during the Battle of the Coral Sea.

"I used to tell him he had nine lives," said his widow, Jo Ann Olsen. "He was really lucky."