The Obama administration acknowledged for the first time that four U.S. citizens have been killed in drone strikes since 2009 in Pakistan and Yemen. The disclosure to Congress on Wednesday comes on the eve of a major national security speech by President Barack Obama.

In conducting U.S. counterterrorism operations against al-Qaida and its associated forces, the government has targeted and killed one citizen, Anwar al-Awlaki, and is aware of the killing by U.S. drones of three others, Attorney General Eric Holder said in a letter to Senate Judiciary Committee Chairman Patrick Leahy.

Al-Awlaki, a radical Muslim cleric, was killed in a drone strike in September 2011 in Yemen. Holder said three other citizens were killed by drones in counterterrorism operations since 2009 but were not targeted. The three are Samir Khan, who was killed in the same drone strike as al-Awlaki; al-Awlaki's 16-year-old son, Abdulrahman, who also was killed in Yemen two weeks later; and Jude Kenan Mohammed, who was killed in a drone strike in Pakistan.

"Since entering office, the president has made clear his commitment to providing Congress and the American people with as much information as possible about our sensitive counterterrorism operations," Holder told Leahy. "To this end, the president has directed me to disclose certain information that until now has been properly classified."

"The administration is determined to continue these extensive outreach efforts to communicate with the American people," Holder wrote.