WASHINGTON — Obama administration lawyers have asserted that it would be lawful to kill a United States citizen if “an informed, high-level official” of the government decided that the target was a ranking figure in Al Qaeda who posed “an imminent threat of violent attack against the United States” and if his capture was not feasible, according to a 16-page document made public on Monday.

The unsigned and undated Justice Department “white paper,” obtained by NBC News, is the most detailed analysis yet to come into public view regarding the Obama legal team’s views about the lawfulness of killing, without a trial, an American citizen who executive branch officials decide is an operational leader of Al Qaeda or one of its allies.

The paper is not the classified memorandum in which the Justice Department’s Office of Legal Counsel signed off on the killing of Anwar al-Awlaki, a radical Muslim cleric who was born in New Mexico and who died in an American drone strike in Yemen in September 2011. But its legal analysis — citing a national right to self-defense as well as the laws of war — closely tracks the rationale in that document, as described to The New York Times in October 2011 by people who had read it.

The memo appears to be a briefing paper that was derived from the real legal memorandum in late 2011 and provided to some members of Congress. It does not discuss any specific target and emphasizes that it does not go into the specific thresholds of evidence that are deemed sufficient.