WASHINGTON, Sept 6, 2007 (AFP) - Osama Bin Laden plans to emerge from the shadows to taunt the United Stages again in a video message marking the sixth anniversary of the September 11 attacks, US-based monitoring services said on Thursday.

The video message from the world's most wanted man would be the first such appearance by the Saudi extremist since October 2004, when he threatened new attacks against the United States just days before a US election.

"The SITE Intelligence Group has learned that a new video message is forthcoming from the head of Al-Qaeda" on the 9/11 anniversary, said the group, which monitors extremist websites and publications.

The Al-Qaeda network's media arm announced the video in a notice posted on jihadist forums at about 5:15 pm (2115 GMT), according to SITE.

Bin Laden has avoided capture since the 9/11 attacks on New York and Washington that killed nearly 3,000 people and jolted American society. He has since inspired an eruption of anti-Western terrorism and his Al-Qaeda network has repeatedly threatened to attack US targets again.

Bush declared a "war on terror" and said he wanted Bin Laden "dead or alive" but the Al-Qaeda chief disappeared after the US-led invasion of Afghanistan to topple Bin Laden's Taliban allies.

Widely believed to have slipped away during a December 2001 battle in Afghanistan's Tora Bora mountains, he is now suspected of hiding somewhere in the remote tribal areas along the Pakistan-Afghanistan border.

Thursday's online notice included a photo of Bin Laden in which his black beard did not have the usual streaks of gray. He was also not wearing a camouflage jacket as in previous appearances.

Another US-based monitor of extremist or jihadist websites, IntelCenter, confirmed the notice from Al-Qaeda's media production group, as-Sahab.

"We expect the release to occur within the next 72 hours," IntelCenter said in a statement.

While some Al-Qaeda figures appear often in video messages, Bin Laden has only issued audio statements for the past three years.

"Bin Laden's appearance is much more infrequent, so any message from him is greeted with much fanfare from the jihadist community," Adam Raisman, senior analyst at SITE, told AFP.

Al-Qaeda and similar groups often use online notices that resemble advertisements to tell supporters of upcoming events, Raisman said.

"This is how jihadist forums work, where the members are notified when they go to the forum of what they can look forward to," he said.

In his 2004 video, Bin Laden told Americans that President George W. Bush "is still misleading you."

Born in Jeddah as the 12th son of construction magnet Mohammad bin Aaud Bin Laden, Osama Bin Laden by his own account was transformed in Afghanistan when fighting the Soviet occupation -- embracing the idea of Muslims uniting against the West.

In Afghanistan, he eventually commanded and financed his own brigade of militants from across the Arab world that later evolved into Al-Qaeda, or "The Base."