WASHINGTON -- Civil and human rights advocates Tuesday denounced a leaked Obama administration “white paper” that sets out the legal justification for killing U.S. citizens suspected of being members of al Qaida, an issue certain to arise during the confirmation hearing Thursday of White House counterterrorism adviser John Brennan to be CIA director.

The White House on Tuesday defended the practice of targeted killing, for which Brennan is a key overseer, as “legal . . . ethical and . . . wise.” But spokesman Jay Carney rejected anew calls by lawmakers and others for the administration to release a secret 2010 Justice Department legal opinion on which the leaked Justice Department white paper was based.

Sen. Dianne Feinstein, D-Calif., who chairs the Senate Intelligence Committee that will consider Brennan’s nomination, acknowledged that the panel had received the white paper as a “confidential document” in June.

The memo has allowed the committee “to conduct appropriate and probing insight into the use of lethal force,” and its release permits the public to “review and judge the legality of these operations,” she said.

At the same time, she said the panel will continue pressing for the secret legal opinion written by the Justice Department’s Office of Legal Counsel, which she said contains “details not outlined in this particular white paper.”

Separately, eight Democratic and three Republican senators sent a letter on Monday to President Barack Obama asking that he give Congress “any and all legal opinions that lay out the executive branch’s official understanding of the president’s authority to deliberately kill Americans.”

The Obama administration has refused for years to make public the legal opinion on which it has based its use of unmanned drones to target American citizens it accuses of being affiliated with al Qaida, most notably Anwar al Awlaki, the spiritual leader of al Qaida’s Yemen affiliate.

The 16-page Justice Department white paper became public late Monday after it was leaked to NBC News. It asserts that the government has the constitutional power to kill a U.S. citizen who is believed to be a leader of al Qaida or an “associated force” and is in another country “actively engaged in planning operations to kill Americans.”

The unclassified and undated memo says that three conditions must be met. “An informed, high-level official of the U.S. government has determined that the targeted individual poses an imminent threat of violent attack against the United States; (2) capture is infeasible, and the United States continues to monitor whether capture becomes feasible, and (3) the operation would be conducted in a manner consistent with applicable law of war principles,” the memo says.

Civil and human rights experts said the paper jumbles international and U.S. law. They also rejected the administration’s assertion that the president’s sweeping authority to kill Americans abroad is beyond court review as well as what they called an exaggerated rewrite of the legal definition of imminent threat.

“The government just gets to make decisions in secret,” said Andrea Prasow, senior counterterrorism counsel for Human Rights Watch.

The administration received a vote of confidence from Rep. Mike Rogers, R-Mich., a former FBI agent who chairs the House Intelligence Committee.