"Mohammed Atta, an Egyptian national, came with Abu Ammer [who is unidentified] and we hosted him in Abu Nidal's house at Al-Dora under our direct supervision," the document states. "We arranged a work program for him for three days with a team dedicated to working with him ... He displayed extraordinary effort and showed a firm commitment to lead the team which will be responsible for attacking the targets that we have agreed to destroy."

The document, which according to Coughlin was supplied by Iraq's interim government, doesn't say exactly when Atta was supposed to have actually flown to Baghdad. But the memo is dated July 1, 2001, and Coughlin himself places the trip as the summer of 2001.

The problem with this, say U.S. law enforcement officials, is that the FBI has compiled a highly detailed time line for Atta's movements throughout the spring and summer of 2001 based on a mountain of documentary evidence, including airline records, ATM withdrawals and hotel receipts. Those records show Atta crisscrossing the United States during this period--making only one overseas trip, an 11-day visit to Spain that didn't begin until six days after the date of the Iraqi memo.

One FBI document, labeled "Law Enforcement Sensitive," states that during the summer of 2001, Atta "conducted extensive travel" that included visits in Florida, Boston, New York, New Jersey and Las Vegas. Indeed, this and other FBI documents show that during the last few days in June--when the presumed Iraq trip would appear to have occurred--almost all of Atta's movements are accounted for: On June 27, 2001, Atta flew from Ft. Lauderdale, Fla., to Boston. On the morning of June 28, he traveled from Boston to San Francisco (flying first class) where he switched planes and landed in Las Vegas that afternoon at 2:41 p.m. That afternoon, he rented a Chevrolet Malibu from an Alamo rental-car office, set up an account at an Internet cafe called the Cyber Zone and checked into the EconoLodge motel on Las Vegas Boulevard, a cheap motel in a neighborhood of seedy strip joints that is located barely two blocks from the local FBI office.

The FBI records show Atta logged onto his Cyber Zone Internet account five times over the next two days and then checked out of the EconoLodge at 3:30 a.m. on the morning of July 1. He then returned his rental car and boarded a flight to Denver at 5:59 a.m., landing in Boston later that day. A week later, on July 7, Atta boarded a flight from Boston to Zurich--the first leg on his trip to Spain. He returned to the United States on July 19, 2001.

Much about Atta's movements is still unknown--and most likely will remain so. FBI officials believe, for example, that Atta flew to Las Vegas as part of a series of trips he took that summer to test security at U.S. airports in preparation for the September 11 attacks. But it is just a theory. The visit to Spain is believed to have been for a meeting with Ramzi bin al-Shibh, one of the planners of the September 11 attacks, who also was in Spain during the same time.