The program was designed in the frantic weeks after the Sept. 11 attacks when President Bush signed a secret order authorizing the C.I.A. to capture or kill Qaeda operatives around the world. To be able to kill Osama bin Laden or his top deputies wherever they might be — even in cities or countries far from a war zone — struck top officials as an urgent goal, according to people involved in the discussions.
But in practice, creating and training the teams proved to be difficult.
“It sounds great in the movies, but when you try to do it it’s not that easy,” said one former intelligence official. “Where do you base them? What do they look like? Are they going to be sitting around at headquarters on 24-hour alert waiting to be called?”
A C.I.A. spokesman declined to comment for this article.
There has been intense speculation about the nature of the program since members of the House Intelligence Committee disclosed last week that Mr. Panetta had put an end to it. The Wall Street Journal reported on Monday that the secret program was intended to capture or kill senior Qaeda leaders.
Current and former officials said that the program was designed as a more “surgical” solution to eliminating terrorists than missile strikes with armed Predator drones, which cannot be used in cities and have occasionally resulted in dozens of civilian casualties.
“The Predator strikes have been successful, and I was pleased to see the Obama administration continue them,” said Senator Christopher S. Bond of Missouri, the top Republican on the Senate Intelligence Committee. “This was another effort that was trying to accomplish the same objective.”
Senator Bond would not discuss specific details about the terminated C.I.A. program.
It is not clear why Mr. Panetta decided to cancel the program, although several current and former government officials said that the program never developed beyond vague concepts. The C.I.A. never proposed a specific operation to the White House for approval, said the officials, who would only speak anonymously because the program had been classified.
Because the program was only nascent, and because Congress had already signed off on the C.I.A.’s broad authoritiesafter the Sept. 11 attacks, the officials and some Republican lawmakers said that the spy agency was not required to brief lawmakers on specifics about the program.
But Congressional Democrats were furious that the program had not been shared with the committees. The Senate and House oversight committees had been created by law in the 1970s as a direct response to disclosures of C.I.A. abuses, notably including assassination plots against Patrice Lumumba in the Congo, Fidel Castro in Cuba, and other foreign politicians. In addition, President Gerald Ford in 1976 issued an executive order banning assassinations.
But the ban does not apply to the killing of enemies in a war. . The Bush administration took the position that killing members of Al Qaeda, a terrorist group that has attacked the United States and stated that its goal is to attack again, is no different than shooting enemy soldiers on the battlefield. The Obama administration, which has continued to fire missiles from Predator drones on suspected Qaeda members in Pakistan, has taken the same view.
Kenneth Anderson, a law professor at American University who has studied targeted killings, said the United States first made the argument in 1989 that killing terrorists would not violate the assassination ban and would be a legal act of self-defense under international law. The killings would be premised on the condition that authorities in the country where the terrorist was located were unable or unwilling to stop the terrorist , he said.