WASHINGTON -- President Barack Obama on Wednesday ordered the Justice Department to share with Congress a classified memo that explains the legal rationale that justifies the targeted killing of Americans suspected of being members of al Qaida.

The decision came after years of refusing to make the memo available and two days after a Justice Department "white paper" that described the memo’s contents was made public. The memo provides the legal framework for U.S. drone attacks that have killed at least three American citizens and as many as 3,500 others.

Obama’s counter terrorism adviser, John Brennan, Obama’s nominee to head the CIA, is expected to face tough questioning over the program Thursday from the Senate Intelligence Committee considering his nomination.

“Today, as part of the president’s ongoing commitment to consult with Congress on national security matters, the president directed the Department of Justice to provide the congressional intelligence committees access to classified Office of Legal Counsel advice related to the subject of the Department of Justice white paper,” the White House said in a statement emailed to reporters.

A further explanation provided by the White House said Obama made the decision in an effort to include Congress in discussion of the country’s counterterrorism policies. The explanation called the decision "an extraordinary action."

Targeted killing, which began under former President George W. Bush, officially remains a classified CIA program. To date, it is known to involve only missile strikes by unmanned aircraft in Pakistan, Somalia and Yemen against what U.S. officials say are leaders of al Qaida and “associated groups” plotting imminent attacks on U.S. targets.

The Obama administration repeatedly has denied requests that the memo justifying the program be released and has fought in court to keep it secret. In December, a federal judge in Manhattan rejected a request that the memo be made public under the country’s Freedom of Information Act.

A bipartisan coalition in Congress that includes both liberal Democrats and conservative Republicans nevertheless have demanded that the memo be made public, most recently on Monday when three Republican and eight Democratic senators wrote the president asking that he share the memo.

Obama’s decision to allow members of the House and Senate intelligence committees to see the memo came after the publication of a so-called "white paper" that described the reasoning behind the Justice Department memo. U.S. Sen. Dianne Feinstein, D-Calif., chairwoman of the Senate Intelligence Committee, said the 16-page white paper had been provided to her committee last June and had provided the background the committee needed to oversee the drone program. The memo leaked to NBC News, which published it Monday.

Critics of the drone program immediately attacked the logic described in the paper, saying it relied on a misinterpretation of both U.S. and international law, and misconstrued the definition of "imminent" in its search to justify the killing of people who had not been accused of a crime.

The paper 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.”