Updated

Usama bin Laden's terror network could be preparing another major attack on a target in the United States or Europe as soon as the end of this year, a French terrorism expert said Friday.

In Britain, the head of Scotland Yard's anti-terrorist unit also warned of possible attacks, saying lone bombers and gunmen unconnected to Al Qaeda could use Wednesday's anniversary as a world stage for their causes and strike in Britain.

"We shouldn't underestimate these individuals. An individual is not incapable of causing serious impact and that is something we are alert to. Our intention is to enhance the deterrent," said Scotland Yard's David Veness, adding that he knew of no specific threats to Britain.

In Paris, Roland Jacquard, director of the International Observatory on Terrorism and a consultant to the French government, estimated it would take between a year and 16 months after the Sept. 11 attacks for Al Qaeda to prepare for another operation.

"It's likely the organization will be ready to make an attack at the end of the year or the beginning of next year," said Jacquard, who has written a biography of bin Laden.

Jacquard said Al Qaeda had countless terrorist plans at its disposal, including some for this year that could have involved accused Sept. 11 conspirator Zacarias Moussaoui.

ABC News, quoting French intelligence authorities, reported Friday that Moussaoui was to be part of a second wave of suicide hijackings planned for early 2002, and that authorities' efforts to link him to the Sept. 11 plot were a mistake.

But Jacquard, whose latest book is titled The Secret Archives of al-Qaida, said it was difficult to tell what Moussaoui's precise role was or whether he was meant to be one of the Sept. 11 hijackers.

He said, however, that Moussaoui was in contact with Al Qaeda-linked groups in Europe and Malaysia, and could have been a type of "replacement player" for the World Trade Center attack if one of the hijackers was unable to participate.

Moussaoui, a French citizen of Moroccan descent, was arrested in August 2001, nearly a month before the World Trade Center attack. He could face the death penalty if convicted on charges he participated in the Sept. 11 plot.

In an interview, Jacquard said Al Qaeda had plans for attacks using pesticide planes in the United States and a third wave of attacks against landmarks in Europe.

"They wanted also to plan some terrorist attacks with chemical arms and biological arms against even ... Notre Dame in Paris, and probably some other targets in London," he said, adding that other possible targets were in Strasbourg, in eastern France.

The preparations for the attacks included poison tests on live subjects such as rabbits, dogs and even human volunteers, he said.

The rout of the Taliban government in Afghanistan has robbed Al Qaeda of crucial diplomatic and logistical support, disrupted its communications systems and deprived it of some of its leaders, Jacquard said.

But Al Qaeda "is still working and they still have a lot of plans," he said.

In London, Veness said mobile armed road blocks will be in place around London as a first point of defense on Sept. 11.

He said an individual attack could be anything from a suicide bomber to a traditional gun, bomb or hijack attempt.

"What we are suggesting is there is particular concern or vulnerability over this period which includes individuals attacking alone," he said.