As part of the macabre ritual the staff members look at the footage of drone strikes in Pakistan and other countries and a sampling of the intelligence buttressing each strike, but not the internal C.I.A. cables discussing the attacks and their aftermath. The screenings have provided a veneer of congressional oversight and have led lawmakers to claim that the targeted killing program is subject to rigorous review, to defend it vigorously in public and to authorize its sizable budget each year.

That unwavering support from Capitol Hill is but one reason the C.I.A.’s killing missions are embedded in American warfare and unlikely to change significantly despite President Obama’s announcement on Thursday that a drone strike accidentally killed two innocent hostages, an American and an Italian. The program is under fire like never before, but the White House continues to champion it, and C.I.A. officers who built the program more than a decade ago — some of whom also led the C.I.A. detention program that used torture in secret prisons — have ascended to the agency’s powerful senior ranks.

Although lawmakers insist that there is great accountability to the program, interviews with administration and congressional officials show that Congress holds the program to less careful scrutiny than many members assert. Top C.I.A. officials, who learned the importance of cultivating Congress after the resistance they ran into on the detention program, have dug in to protect the agency’s drone operations, frustrating a pledge by Mr. Obama two years ago to overhaul the program and pull it from the shadows.