Zawahiri is thought to be in hiding on the Afghan-Pakistan border

Advertisements posted on Jihadist websites said questions sent to them over the next month would be passed to al-Qaeda's deputy leader for his reply.

It said the questions would be sent "without alteration, whether it comes from someone who agrees or disagrees".

The offer also came at the end of an interview by Zawahiri posted on Sunday.

In the video, also produced by al-Sahab, Zawahiri said the US-led coalition in Iraq was "defeated and looking for a way out" and said the decision of UK forces to "flee" Basra showed insurgents were gaining strength.

Iraq took formal responsibility for security in Basra province on Sunday, four-and-a-half years after the invasion.

'Brief and focused'

The adverts published by al-Sahab invited "individuals, organisations and media establishments" to submit questions for an "open interview" with Zawahiri by sending them by 16 January to the websites where it usually posts its messages.

It shows how this group with 7th Century ideology is exploiting 21st Century media capabilities

Bruce Hoffman

Georgetown University

"Care should be taken in making the questions brief and focused," the advert asked.

"We also ask the brothers, the supervisors [of the websites] to collect the questions and transmit them without alteration, whether it is comes from someone who agrees or disagrees," it added.

The advert finished with al-Sahab saying that "with God's help and support" it will try to publish Zawahiri's answers to the questions "as soon as possible".

Egyptian-born Zawahiri has emerged as al-Qaeda's most prominent spokesman in recent years, appearing in at least 16 videos and audiotapes this year - four times as many as its leader, Osama Bin Laden.

The invitation is the first to have been issued by an al-Qaeda leader

The two have evaded capture since US-led forces overthrew the Taleban in Afghanistan following the 11 September 2001 attacks on the US. They are thought to be hiding on the Afghan-Pakistan border.

IntelCenter, an organisation which monitors Jihadist websites, said the invitation was the first to have been issued by a high-ranking al-Qaeda leader.

Bruce Hoffman, a terrorism expert at Georgetown University in Washington DC, said al-Qaeda wanted to "look more cutting-edge and give the perception of greater legitimacy".

"It shows how this group with 7th Century ideology is exploiting 21st Century media capabilities," he told the Associated Press.

Mr Hoffman said it also revealed that Zawahiri was trying to portray himself more like a true leader than a "homicidal thug" by opening himself up to questioning in a similar fashion to televised political debates.