He also handed over the bomb, designed by the group’s top explosives expert to be undetectable at airport security checks, to the F.B.I., which is analyzing its properties at its laboratory at Quantico, Va. The agent is now safe in Saudi Arabia, officials said. The bombing plot was kept secret for weeks by the C.I.A. and other agencies because they feared retaliation against the agent and his family — not, as some commentators have suggested, because the Obama administration wanted to schedule an announcement of the foiled plot, American officials said.

Officials said Tuesday night that the risk to the agent and his relatives had now been “mitigated,” evidently by moving both him and his family to safe locations.

But American intelligence officials were angry about the disclosure of the Qaeda plot, first reported Monday by The Associated Press, which had held the story for several days at the request of the C.I.A. They feared the leak would discourage foreign intelligence services from cooperating with the United States on risky missions in the future, said Representative Peter T. King, a New York Republican and chairman of the House Homeland Security Committee.

“We are talking about compromising methods and sources and causing our partners to be leery about working with us,” said Mr. King, who spoke with reporters about the plot on Monday night and Tuesday after he was briefed by counterterrorism officials. Mr. King, who called the bomb plot “one of the most tightly held operations I’ve seen in my years in the House,” said he was told that government officials planned to investigate the source of the original leak. The C.I.A. declined to comment.

Intelligence officials believe that the explosive is the latest effort of the group’s skilled bomb maker, Ibrahim Hassan al-Asiri. Mr. Asiri is also believed to have designed the explosives used in the failed bombing attempt on an airliner over Detroit on Dec. 25, 2009, and packed into printer cartridges and placed on cargo planes in October 2010.