Anwar al-Awlaki, who has dual U.S.-Yemeni citizenship, was involved in “preparing” Umar Farouk Abdulmutallab in the attempted midflight bombing of a Northwest Airlines jet traveling from Amsterdam to Detroit on Dec. 25, Director of National IntelligenceJames R. Clapper said in a court statement made public on Saturday.

In addition, as a leader of the Yemen-based terror group Al Qaeda in the Arabian Peninsula, Mr. al-Awlaki has played a key role since late 2009 in “planning attacks on U.S. interests,” Mr. Clapper said.

“In November 2009, while in Yemen, Mr. Abdulmutallab swore allegiance to the emir of [AQAP] and shortly thereafter received instructions from Mr. al-Awlaki to detonate an explosive device aboard a U.S. airplane over U.S. airspace,” the intelligence director stated.

It marks the first time Mr. al-Awlaki‘s direct role in instructing the suspect in the airline bombing plot and his group’s other plots were made public. In July, Michael E. Leiter, head of the National Counterterrorism Center, said Mr. al-Awlaki was directly involved in the airline plot, but he did not provide details.

Mr. Clapper did not say how U.S. intelligence learned of the links between Mr. al-Awlaki and Mr. Abdulmutallab.

However, a Senate intelligence committee report on intelligence failures related to the attempted airline bombing revealed in May that the National Security Agency partially identified Mr. Abdulmutallab as a terrorist but failed to spy more intently on him, a likely reference to intercepted communications between the two men.

Mr. Clapper also linked the Yemen-based group to the suicide bombing that nearly killed Saudi Arabia‘s assistant interior minister, Prince Mohammed bin Nayef, in August 2009. That blast was carried out by a Saudi national who detonated a bomb hidden in his rectum during a reception for the prince.

Additionally, Mr. Clapper‘s statement said Mr. al-Awlaki‘s group was behind the suicide bombing that killed four South Korean tourists in Yemen in March 2009 and the attempted assassination of the British ambassador to Yemen in April.

The statement was issued as part of the U.S. government‘s motion opposing a lawsuit brought by the American Civil Liberties Union on behalf of Mr. al-Awlaki‘s father, Nasser al-Awlaki, that sought to remove the cleric from a CIA and U.S. military target list of terrorists to be killed or captured.

The Justice Department, in its motion, invoked the state secrets privilege in opposing the lawsuit and included statements from CIA Director Leon Panetta and Defense Secretary Robert M. Gates.

Mr. Clapper said in his statement that while some information on al Qaeda and Mr. al-Awlaki has been made public, the suit would involve secrets that must not be disclosed.

According to Mr. Clapper, Mr. al-Awlaki “pledged an oath of loyalty to AQAP emir Nasir al-Washishi and “is playing a key role in setting the strategic direction” for the group.

“Al-Awlaki has also recruited individuals to join AQAP, facilitated training at camps in Yemen in support of acts of terrorism, and helped focus AQAP’s attention on planning attacks on U.S. interests,” he said.

Since late 2009, Mr. al-Awlaki “has taken on an increasingly operational role in AQAP, including preparing” Mr. Abdulmutallab for the airline bombing attempt, he said.

The statement noted Mr. al-Awlaki‘s May 23 interview in an al Qaeda video in which he stated, “My message to the Muslims in general, and to those in the Arabian Peninsula in particular, is that we should participate in this jihad against America.”

About the Christmas Day plot, Mr. al-Awlaki said that “no one should even ask us about targeting a bunch of Americans who would have been killed in an airplane. Our unsettled account with America includes, at the very least, 1 million women and children. I’m not even talking about the men. Our unsettled account with America, in women and children alone, has exceeded 1 million. Those who would have been killed in the plane are a drop in the ocean.”

Mr. Clapper‘s statement did not link Mr. al-Awlaki to Army Maj. Nidal M. Hasan, who is accused of killing 13 people and wounding 32 others in a shooting at Fort Hood, Texas.

However, the statement noted that Mr. al-Awlaki praised the shooting and the attempted airline bombing in his interview in May.

Other U.S. officials have said the FBI had obtained e-mails between Maj. Hasan and Mr. al-Awlaki before the shooting but did not take action against the Army psychiatric counselor.

A U.S. official knowledgeable about Mr. al-Awlaki said that, in addition his growing role in terror operations, he continues as a “provocateur and propagandist trying to inspire would be jihadis worldwide, such as Faisal Shahzad,” who tried to set off a car bomb in New York’s Times Square.

“He has spoken publicly and proudly about his desire to kill American men, women and children, so there should be no doubt about his intentions,” the official said. “He wears a terrorist coat of many colors, but mostly red.”

Mr. Gates said in his statement that the lawsuit would require disclosure of classified information about U.S. military efforts against terrorists as well as communications used in tracking al Qaeda‘s activities in Yemen.

The defense secretary said that making public information about U.S. military planning overseas and the collection of intelligence on al Qaeda “could not only allow foreign terrorist organizations to adjust their plans based on the state of U.S. knowledge, but alter their communications and activities and thereby shield information that could prove critical to assessing the threat they pose to the United States and other nations.”