The radical Yemeni American cleric who was killed in a CIA drone strike in Yemen in September personally directed the plot to take down a plane over Detroit on Christmas Day 2009, according to a Justice Department memo.

The memo, released Friday ahead of the sentencing next week of Umar Farouk Abdulmutallab, the so-called “underwear bomber,” offers the most detailed evidence to date of Anwar al-Awlaki’s operational role in al-Qaeda’s Yemeni affiliate.

As far back as 2009, investigators had linked Abdulmutallab with Awlaki, but the memo describes how the Yemeni American tested the Nigerian’s commitment to jihad, arranged for him to meet a bomb-maker, and told him to get on a U.S. airliner and detonate his explosives over the United States.

Abdulmutallab, 25, pleaded guilty in October to eight charges, including attempted murder and terrorism, for attempting to take down a flight from Amsterdam. He is scheduled to be sentenced next week in U.S. District Court in Detroit, where prosecutors are seeking consecutive life sentences on several counts.

The memo, as well as supplements to it that describe Abdulmutallab’s movements and motivation, is designed to persuade a judge to impose the maximum sentence.

One supplement describes how Abdulmutallab, inspired by the online lectures of Awlaki, left Dubai, United Arab Emirates, where he was taking graduate classes, and traveled to Yemen to meet the cleric in August 2009. By that time, Abdulmutallab had been following Awlaki, the preeminent propagandist of al-Qaeda in the Arabian Peninsula, for several years and was determined to carry out a suicide operation.

In Yemen, he immediately began to visit mosques to ask people how he could get in touch with Awlaki, who was in hiding. An unnamed individual told Awlaki of the inquiries, and the cleric sent him a text message asking him to call, according to the memo.

Awlaki requested a written explanation of why Abdulmutallab wanted to become involved in violent jihad. The cleric, apparently satisfied with the message, told Abdulmutallab he would find a way for him to participate, the memo stated.

The description of Abdulmutallab’s movements is based on several debriefing statements he gave to FBI agents between January and April 2010. The Obama administration was criticized by some Republicans for the FBI’s decision to give a Miranda warning to Abdulmutallab less than an hour after he was initially questioned on Dec. 25, 2009. But the Justice Department memo indicates that he continued to speak to the FBI and provided details about the plot and senior al-Qaeda figures.

“I think this should put to rest the suggestion that he didn’t provide useful information,” said an administration official, who spoke on condition of anonymity to discuss the case before sentencing.

What is unclear is whether any of that information provided intelligence that led to the targeting of Awlaki in a joint CIA-Special Operations strike in September, the first deliberate killing of a U.S. citizen in a counterterrorism operation.

The administration official would not discuss the specific intelligence behind the killing of Awlaki, an operation that remains classified, but said Abdulmutallab’s information was a “piece of the puzzle.”

A second U.S. citizen, Samir Khan, was killed in the strike, although he was not a primary target, officials said. Awlaki’s 16-year-old son was also killed in a drone strike several weeks after the death of his father.

A secret Justice Department memo justified the killing of the elder Awlaki, and the Obama administration has been under pressure from civil liberties groups and lawmakers to release the memo and its legal rationale for the killing.

According to the memo released Friday, Abdulmutallab, after establishing contact with Awlaki, was driven “through the Yemeni desert” to the cleric’s house, where he stayed for three days.

“During that time, defendant met with Awlaki and the two men discussed martyrdom and jihad,” the memo stated. “Awlaki told defendant that jihad requires patience but comes with many rewards.”Abdulmutallab was taken from Awlaki’s house to meet Ibrahim al-Asiri, a feared bomb-maker who had designed a device that was able to beat normal screenings at airports.After leaving Yemen, Abdulmutallab traveled undetected with the device in his underwear from Yemen to Ethiopia to Ghana to Nigeria to Amsterdam before boarding the flight to Detroit. Asiri discussed the planned attack with Awlaki, who gave it his final approval, according to the memo. For two weeks, Abdulmutallab trained in an al-Qaeda in the Arabian Peninsula, or AQAP, camp and received instruction in weapons. He met Khan at the camp, the memo said.

Asiri trained Abdulmutallab, showing him how to detonate the bomb. By pushing a syringe, two chemicals would mix and spark a fire, which would set off an explosion. As the plane carrying 289 people approached the U.S.-Canadian border, Abdulmutallab went to the bathroom, washed his face, brushed his teeth and put on cologne to purify himself before death. But the device, which had no metal parts, malfunctioned. After his clothing caught fire, Abdulmutallab was overpowered in his seat by other passengers.

In a text message to his family three months before the planned attack, Abdulmutallab sounded ready to die, saying: “Oh mother don’t despair or worry and never lose hope in the mercy of Allah. . . . May Allah make it a successful and happy event for you all, amen.”

Staff researcher Julie Tate contributed to this report.