A radical US-born Yemeni Islamist cleric has called for the killing of Americans in a new video message posted on radical web sites.
Anwar al-Awlaki said no permission was needed to kill Americans as they are from the "party of devils".
It comes shortly after authorities intercepted air cargo bombs sent from Yemen to the US in a plot linked to Mr Awlaki.
The US has named Mr Awlaki a "specially designated global terrorist".
Investigators have linked Mr Awlaki to the US army base killings in Fort Hood, Texas, last year's Christmas airline bomb attempt, and the failed Times Square bombing in New York.
US officials say he is a leader of al-Qaeda in the Arabian Peninsula, an offshoot of the militant network based in Saudi Arabia and Yemen.
'Leaders are corrupt'
In the 23-minute message posted on Monday, Mr Awlaki called all Arab and Yemeni leaders "corrupt".
"Kings, emirs, and presidents are not now qualified to lead the nation, or even a flock of sheep," he said.
"If the leaders are corrupt, the scholars have the responsibility to lead the nation."
He was shown seated at a desk, wearing traditional Yemeni clothes with a dagger in his belt.
Last week, YouTube removed hundreds of clips of Anwar al-Awlaki's calls to jihad saying they violated a ban on hate speech and incitement to violence.
Last month, investigators working for New York Congressman Anthony Weiner, a Democrat, reported finding more than 700 videos in which Mr Awlaki appeared. The clips had garnered more than 3.5m hits.
Mr Awlaki, an American-born cleric of Yemeni descent, is said to be on a CIA hit list authorised by President Barack Obama.
In July, the US treasury department put Mr Awlaki on its terrorism blacklist and imposed financial sanctions on him.
US officials say Mr Awlaki helped recruit Umar Farouk Abdulmutallab, the Nigerian accused of attempting to blow up an airliner as it flew into Detroit on 25 December 2009.
Maj Nidal Hasan, the US Army psychiatrist accused of killing 13 comrades in the Fort Hood shooting last year, sought religious advice from Mr Awlaki and saw him preach in the US state of Virginia in 2001, US officials say.
A student found guilty of attempting to murder MP Stephen Timms in east London was said to have been inspired by Mr Awlaki's online sermons.