The Obama administration approved the targeted killing of Anwar al-Awlaki, 38, an American citizen born to Yemini parents in New Mexico, who spent many years serving as an imam (Muslim cleric) in the U.S, counterterrorism officiays said.

Al-Awlaki, who is thought to be hiding in the mountains of Yemen, has been linked to U.S. Army psychiatrist Maj. Nidal Malik Hasan, who opened fire last November on soldiers at Ft. Hood in Texas, killing 13 of them.

U.S. Intelligence agents also believe al-Awlaki had been in contact with Umar Farouk Abdulmutallab, the Nigerian student who tried to detonate explosives on a Northwest passenger jet during its approach to the Detroit airport on Christmas Day.

At a House hearing in February, Intelligence chief Dennis C. Blair said targeting an American citizen was possible.

"We take direct actions against terrorists in the Intelligence committee," Blair said. "If we think that direct action will involve killing an American, we get specific permission to do that," he said.

In January, the Lost Angeles Times reported that al-Awlaki could be targeted, and on Tuesday, Reuters reported that his name had been added to a list of terrorists the government would like to capture or assassinate.

"The danger Awlaki poses to this country is no longer confined to words," a U.S. official told the New York Times on condition of anonymity.

"The United States works exactly as the American people expect - to overcome threats to their security, and this individual - through his own actions - has become one. Awlaki knows what he's done and he knows he won't be met with handshakes and flowers. None of this should surprise anyone," he said.

Al-Alwaki's lectures on the Koran and Islamic theology are especially popular among English-speaking Muslims.

U.S. officials believe he has shifted from encouraging his followers to jihad ("holy" war) to recruiting and planning attacks on Americans both in the U.S. and abroad.