The US government has authorised the capture or killing of radical Muslim cleric Anwar al-Awlaki, currently based in Yemen, officials have confirmed.
The cleric, who is a US citizen, is being targeted for his involvement in planning attacks on the US.
Mr Awlaki was linked to the attempted bombing of an airliner bound for the US and a shooting on a US Army base.
US officials have warned that Yemen is becoming a safe haven for al-Qaeda militants.
The BBC's Steve Kingstone, in Washington, says it is highly unusual for the CIA to be given approval by the president's National Security Council to target a US citizen.
The order was made by the Obama administration earlier this year, but it has just been revealed after a review of national security policy.
It was first reported in the New York Times and later confirmed to the BBC by US officials.
"Awlaki is a threat to the United States and our allies. He's plotted serious attacks against this country and others. Of course he's a US government target," one official said.
Mr Awlaki was born in New Mexico, and later served as an imam in Colorado, California and Virginia.
He became popular among Islamic radicals for his firebrand preaching in English which endorsed the use of violence as a religious duty.
It was while he was an imam in San Diego that his sermons were attended by two of the 9/11 hijackers.
He fled the US in 2007 and moved to Yemen.
US intelligence previously viewed him as a radical Islamist preacher, but officials say he is now an active recruiter for al-Qaeda in the Arabian Peninsula.
Mr Awlaki has been linked to the suspects in the Fort Hood shootings last November in which 13 people died, and a failed attempt to blow up a transatlantic airliner on Christmas day.
Potentially, a US attack on him could be in the form of an air strike by an unmanned drone, our correspondent says.
The US military already has approval for such killings, based on a congressional authorisation for war with al-Qaeda after the 9/11 attacks on the US.
"Awlaki knows what he's done, and he knows he won't be met with handshakes and flowers. None of this should surprise anyone," the New York Times quoted an official as saying.
The Yemeni government, with support from the US and Saudi Arabia, has bombed suspected al-Qaeda hideouts in the last few months.
But some analysts have warned that Yemen may become a failed state because of the fragile hold the Yemeni government has on its own country.
Umar Farouk Abdulmutallab, the Nigerian man accused of trying to blow up a plane on its way into Detroit airport on Christmas Day 2009, allegedly met Mr Awlaki in Yemen weeks before boarding a US-bound plane in Lagos.