American servicemen aboard the USS Carl Vinson aircraft carrier, which buried Osama bin Laden's body at sea, basked in their history-making mission Sunday but refused to discuss the attack that killed him, reflecting concerns over possible retaliation.

U.S. defense officials are taking measures to ensure the security of the operatives involved in the May 2 assault on a walled compound in Abbottabad, Pakistan, particularly the Navy SEAL team that killed the world's most-wanted terrorist.

The massive aircraft carrier dropped anchor under heavy guard at Manila Bay on Sunday at the start of a four-day routine port and goodwill visit. It's the first break for Carl Vinson's 5,500 sailors, pilots and crew after months of war in Iraq and Afghanistan that was capped by their support to the commando strike that killed bin Laden.

All those aboard the warship were ordered not to discuss operational details as they come into contact with the public for the first time since the covert strike, officials said.

Philippine President Benigno Aquino III, accompanied by senior members of his Cabinet and military chief of staff, were flown to the Carl Vinson on Saturday as it traveled in the South China Sea toward the Philippines, a key Asian anti-terrorism ally. Then a group of journalists were invited the next day.

Discussions about the slain al-Qaida leader were taboo in both visits. American servicemen did not show any overt sign of celebration over their triumph.

Asked how he felt being a part of the history-making mission in Pakistan, Rear Admiral Samuel Perez, who headed the carrier strike force that included the nuclear-powered Carl Vinson, refused to be drawn in.

"You know I'm not going to comment on that," Perez told journalists aboard the 97,000-ton carrier, but added that "everyday that you're a sailor in the U.S. Navy, you're a part of history."

Filipino-American Navy Corpsman Liberty Raposas said morale was "very high" among her colleagues.

Perez said hundreds of servicemen and women who trace their roots to the Philippines welcomed Aquino, who was given a tour of the ship and an exhibition of fighter jets landing and taking off.

Aquino, at one point, sat in the cockpit of an F/A-18E Super Hornet fighter jet in a hangar bay as sailors snapped pictures.

But the one thing on everybody's mind — bin Laden's burial from the Carl Vinson just 12 days earlier — was not raised by either side, Defense Secretary Voltaire Gazmin said.

"We did not ask for a briefing because it was too sensitive," Gazmin told The Associated Press on Sunday. "It was a friendly visit and we let it stay that way."

In impromptu remarks on the ship, Aquino reaffirmed the "historic, defense and cultural ties" between the United States and the Philippines, his spokesman, Ricky Carandang, said.

U.S. forces have been training and arming Filipino soldiers battling al-Qaida-linked militants in the south.

The Carl Vinson came from the North Arabian Sea, where it had received the SEAL team that carried bin Laden's body after his death in his compound near a Pakistani military academy.

Pentagon officials have said that on the carrier, bin Laden's body was placed in a "weighted bag," an officer made religious remarks and the remains were put on a flat board and tipped into the sea.

Defense Secretary Robert Gates has said that during a recent meeting with SEAL members who attacked bin Laden, they expressed concerns about their families' security.

American officials agreed shortly after bin Laden was killed not to release any details on the commando assault, Gates said, but added "that fell apart — the next day."

"We are looking at what measures can be taken to pump up the security," Gates said.

The U.S. Embassy said Carl Vinson's servicemen will take part in sports events and civic projects with Filipino counterparts.

Philippine police have stepped up security in the capital, where left-wing groups have threatened to stage anti-U.S. military protests and al-Qaida-linked militants have previously staged bombings.