The threat posed by Al-Qaeda remains strong, experts say, because as well as planning attacks, Osama bin Laden's organisation is inspiring others.

US President Barack Obama warned on Tuesday that fresh attacks against the United States are currently in preparation, as he announced a massive troop surge in Afghanistan.

NONE Whether they are in direct contact with Al-Qaeda in Pakistan's tribal areas or have been radicalised by the Internet, hundreds of Islamists are ready to act in Bin Laden's name, experts warn.

Jean-Pierre Filiu, of Paris's Sciences Po University, said the danger posed by the Al-Qaeda hierarchy -- what is known as Al-Qaeda Central -- still posed a very real danger.

"This is particularly so because Al-Qaeda -- threatened, cornered, breathless -- has a cruel need to pull off a major attack," he told AFP.

"Paradoxically, an organisation which is losing momentum is more dangerous than one that is cruising."

Marc Sageman, a former CIA agent in Afghanistan and now a psychiatrist and expert on jihadi networks, recently said he had found evidence of 33 radical Islamist plots against the West in the last five years.

Six of these could be attributed to Al-Qaeda Central and two to affiliated groups, he said.

'Considerable ability to do harm'

The remaining 25, Sageman said, were autonomous plots conducted by "homegrown perpetrators" with no connection with formal international groups, but were nevertheless inspired by Al-Qaeda.

NONE "From its sanctuary in Pakistan's tribal areas, (Al-Qaeda) retains a considerable ability to do harm," Filiu said.

"This has been shown by more or less successful terrorist plots in various countries which can be linked in some way back to these (tribal) areas.

"There might only be a hundred or so Al-Qaeda members in Afghanistan, but the heart of the organisation is now beating in the Pakistani tribal areas. This is where the inspiration, the energy and the impetus for the terrorist movement is coming from," Filiu said.

Take the example of Najibullah Zazi, the bus driver living in the US city of Denver who is suspected of planning an attack in New York.

Last year he travelled to Pakistan's tribal regions where is thought to have been trained in using explosives.

Thanks to the Internet, this type of journey is no longer necessary, according to Magnus Ranstrop, of the Centre for Asymmetric Threat Studies at the Swedish National Defence College.

'Real threat'

"There is a real threat from the Al Qaeda core, but at the same time it's becoming more diffuse," he told AFP.

NONE "All you need is a couple of individuals for an attack. There's so much mimicking going on, new ideas that come up.

"Look at the Mumbai attacks: are they going to learn from these attacks and replicate them somewhere, against Western targets? They learn from what works, and they learn from what doesn't work too.

"It can be a major plot, or a very simple attack on tourists, maybe with a simple knife. It's a global brainstorming. They are thinking: 'How can we really surprise them ?'

"A lot of plots, big and small, have a link with the Afghanistan-Pakistan region."

Obama is right to focus on this area, Ranstorp said, but whether the troop surge and change in strategy brings results remains to be seen.