The United States drone aircraft attack that killed two midlevel al-Qaida militants in Yemen on Thursday was targeting the leader of al-Qaida in the Arabian Peninsula, a U.S.-born radical known for encouraging attacks on the United States, U.S. media reported.

CBS News and The Wall Street Journal, citing Yemeni and U.S. officials, said on Friday that Anwar al-Awlaki was not hit when a missile was fired at a car in southern Yemen on Thursday, killing two brothers believed to be al-Qaida militants.

"We were hoping it was him," a U.S. official told CBS News.

The U.S. Defense Department declined to comment on the reports.

Al-Qaida in the Arabian Peninsula, or AQAP, is estimated to number about 300 fighters with strongholds in remote mountain regions in the provinces of Shabwa, Abyan, Jouf and Marib. It is thought to be behind numerous attacks on goverment targets.

The group is said to have inspired attacks by Muslims inside the United States -- including the Fort Hood, Texas, shootings in which an Army psychiatrist is accused of killing
13 people and wounding 32 -- and twice smuggled explosives aboard aircraft headed to the United States.

Yemen's Defense Ministry confirmed Thursday's drone attack had killed two al-Qaida militants, identifying them as brothers Musa'id and Abdullah Mubarak al-Daghari.

Washington considers the Yemen-based al-Qaida branch the world's most active terror cell. With the killing in Pakistan earlier this week of al-Qaida leader Osama bin Laden, some officials believe Awlaki's group now represents the gravest danger to the United States and
other Western nations.