BBC correspondent in Islamabad
American and Pakistani security officials are investigating whether one of eight suspected al-Qaeda men killed during a military operation in Pakistan's tribal region of Waziristan this month is a key terror suspect.
18 suspected militants were held in the tribal areas operation
Habis Abdullah al-Saoub, also known as "Samarkand", is an American national of Jordanian origin and is wanted by the FBI on charges of aiding or assisting al-Qaeda.
Meanwhile, a report in a Pakistani newspaper says another key al-Qaeda man, Ahmed Said al-Kadr, may have slipped out of the tribal area shortly before the start of the military operation.
The identities of the 18 suspected militants detained and the eight killed in the South Waziristan operation have still to be revealed.
The authorities quickly expanded their search and arrest operation to other parts of the tribal belt, and are looking for the tribesmen who may have given protection to suspected al-Qaeda men.
Religious parties have accused the government of victimising the tribesmen, but Information Minister Sheikh Rasheed Ahmed justified the operation by saying one of the dead men could be a prominent al-Qaeda member.
He did not give a name, but a highly informed source in the government told the BBC American security officials believed it could be Samarkand.
The FBI believes he left the United States in October 2001 to join the jihad, or holy war, in Afghanistan.
Reward money of up to $5m has been put up for information leading to his arrest.
Samarkand should not be difficult to identify - the FBI's internet site says he has a three- to five-inch vertical scar on his lower back and a piece of flesh from one of his earlobes is missing.
Meanwhile, a report in the Pakistani newspaper Dawn said the key al-Qaeda suspect, al-Kadr, may have given security forces the slip.
He has been described as a Canadian of Arab origin and a suspected al-Qaeda financier.
There has been no official comment on the newspaper report.