Image caption The US Treasury Department has labelled Anwar al-Awlaki a "specially designated global terrorist"

A US judge has dismissed a lawsuit that sought to halt Washington's alleged programme to capture or kill Americans who join militant groups abroad.

The judge threw out the lawsuit by civil liberties organisations on jurisdictional grounds.

The organisations say they want to halt the alleged programme and reveal the criteria the US government sets for targeting someone.

Washington has not confirmed officially that such a programme exists.

The American Civil Liberties Union (ACLU) and the Center for Constitutional Rights (CCR) had filed the lawsuit on behalf of the father of radical US-born Yemeni Islamist cleric Anwar al-Awlaki, who contacted the groups when his son reportedly appeared on a CIA "capture or kill" list in the summer.

Mr Awlaki, who is thought to be a senior operative for al-Qaeda in Yemen, has been linked to a deadly shooting spree at Fort Hood army base in Texas and an attempted bombing of a US airliner on 25 December 2009.

US District Judge John Bates said the plaintiff lacked legal standing to bring the case and that his claims presented an issue that could not be decided by the courts.

"The serious issues regarding the merits of the alleged authorisation of the targeted killing of a US citizen overseas must await another day or another (non-judicial) forum," the judge said in his ruling.

The ACLU and CCR argue that the American constitution and international law prohibit targeted killings by the US government without charge or conviction.

Anwar al-Awlaki was born in New Mexico and lived in Virginia until the attacks on the World Trade Center and Pentagon on 11 September 2001.

He has posted sermons on the internet thought to have inspired new recruits to Islamist militancy.

He is being sought by the Yemeni authorities, who also reportedly want to capture or kill him.