Sometime in the summer of 1997, an operative for Osama bin Laden sat down at his personal computer in a hideaway in Kenya. He was worried, he wrote in an angry dispatch, about the security of the "East Africa network" of bin Laden, the Saudi exile accused of masterminding a worldwide terrorist conspiracy against Americans.

The organization, the author complained, had declared war against the United States, yet he had learned of that only from the news media. The writer noted with alarm British press reports about the arrest of an aide to bin Laden.Striking almost bureaucratic tones, he said he was worried that "a man with close links" to bin Laden seemed to have "fallen into the enemy's hands." He said the Americans were breathing down the necks of his associates in Nairobi and that he had to take precautions.

"The cell is at 100 percent danger," the operative warned.

Federal authorities believe the writer was Haroun Fazil, who was to become one of the central suspects in the bombing of the American Embassy in Nairobi a year later. The letter was retrieved from a computer in a house where Fazil had been staying, according to papers filed in U.S. District Court in Manhattan.

The papers said the computer was seized in August 1997 in a raid by Kenyan authorities that was attended by an FBI agent. The documents did not make clear whether the FBI had translated and read the document before or after the bombings of the American Embassies in Nairobi and Dar es Salaam, Tanzania, on Aug. 7 this year.

The timing is potentially important because there have been mounting questions since the bombings about whether the United States adequately followed up warnings of a possible terrorist attack on American targets in Kenya.

Fazil eluded American investigators after the bombings. He remains a fugitive.

The dispatch provides a remarkable insight into the workings of a terrorist network in the twilight of the 20th century. The author talks of how he and his fellow operatives follow events on CNN and use the Internet to communicate. He refers to himself as the media information officer of the East Africa cell and complains that he is not being kept in the loop on big decisions.

Along the way, in an almost casual fashion, the document seems to confirm two of the central charges of the federal case against bin Laden: that he had planted a terrorist cell in Nairobi and that his operatives carried out another of the crimes laid at bin Laden's door by federal authorities -- the attacks on American soldiers in Somalia in 1993 and 1994.