Obama's decision on the photos came a day ahead of his planned visit to ground zero in New York City to lay a wreath and visit with 9/11 families and first responders.

It also came after a revised description of the circumstances of bin Laden's death. After initially saying the terrorist was armed or even firing, the White House said Tuesday that bin Laden was unarmed, raising questions about the basis for his killing.

Attorney General Eric Holder, in a congressional appearance, sought to underscore the legality of the shooting.

"Let me make something very clear: The operation in which Osama bin Laden was killed was lawful," Holder told senators Wednesday. The raid "was justified as an action of national self-defense" against "a lawful military target," he said.

Carney said that the SEAL team that raided the compound where bin Laden was living in Abbottabad, Pakistan, had the authority to kill him unless he offered to surrender, in which case the team was required to accept the surrender.

"Consistent with the laws of war, bin Laden's surrender would have been accepted if feasible," said Carney. Officials have said bin Laden resisted, though they have not offered further details.

Meanwhile, the SEALS involved in the daring raid are in the Washington area for debriefing, and US officials have begun to comb through the intelligence trove of computer files, flash drives, DVDs and documents that the commandos hauled out of the terrorist's hideaway.

Bin Laden had about 500 euros sewn into his clothes when he was killed and had phone numbers with him when he was killed, US officials said, a possible indication that the terrorist mastermind was ready to flee his compound on short notice.

Wednesday was not the first time Obama has had to make a consequential decision about releasing photos connected with US troop actions. In 2009 he sought to block the court-ordered release of photos of US troops abusing prisoners in Iraq, a reversal of position that he explained by saying the pictures could inflame anti-American opinion and endanger US forces in Iraq an Afghanistan.