Osama bin Laden's son and heir apparent is no longer under house arrest in Iran and is believed to have joined his father in Pakistan, Director of National Intelligence J. Michael McConnell said Friday.
U.S. counter-terrorism officials said it was unclear whether Saad bin Laden had escaped custody in Iran or was released by the Islamic government. His arrival in Pakistan -- apparently accompanied by other Al Qaeda operatives -- could help replenish the leadership ranks of a terrorist network that has seen at least eight of its senior members killed by CIA missile strikes in recent months.
The younger Bin Laden's departure from Iran comes at a delicate time in relations between Tehran and the United States, with President-elect Barack Obama pledging a new diplomatic approach aimed at defusing long-standing tensions between the two countries.
Saad bin Laden, believed to be in his late 20s, was among as many as 30 senior Al Qaeda figures who were held in custody in Iran over the last six years after fleeing the U.S. invasion of Afghanistan in November 2001.
Bin Laden's departure was reported in September on websites linked to Al Qaeda, but was confirmed for the first time Friday by senior U.S. intelligence officials.
In a session with reporters, McConnell, the outgoing U.S. intelligence chief, said Saad bin Laden "has left Iran. He's not there anymore. He's probably in Pakistan."
In a separate interview, a U.S. counter-terrorism official said Bin Laden was among several Al Qaeda figures who are believed to have moved from Iran to Pakistan last summer.
"It's unclear whether he had Iranian assistance or not," said the official, who spoke on condition of anonymity because he was not authorized to discuss the matter.
The official said it was also not known whether Bin Laden had reunited with his father and whether he had stepped into an operational role in the organization.
"He's obviously there, but what he's doing there remains a little unclear," the official said, adding that Bin Laden is not yet seen as a high-ranking figure in the organization. "He is more of an apprentice. But a dangerous apprentice."
Counter-terrorism experts described Bin Laden's departure from Iran as a disturbing development because of his potential as a successor to his father.
"He is the son closest and most involved in his father's activities," said Bruce Hoffman, a professor at Georgetown University. "He is as extreme as [Osama] Bin Laden, and he is being groomed as a senior member."
Among the others in Iranian custody were Saif Adel, who was an Al Qaeda operations chief, and a former member of Egypt's special forces with long ties to Osama bin Laden. U.S. counter-terrorism officials said it was not clear whether Adel was among those who accompanied Saad bin Laden to Pakistan.
Hoffman said an influx of operatives from Iran "could reverse the recent depletion of Al Qaeda's ranks." He also said their ability to enter Pakistan raised troubling questions about its border security.
In 2003, there were informal negotiations between the United States and Iran over a possible swap of the Al Qaeda prisoners in exchange for members of an Iranian opposition group, the Mujahedin Khalq, who had been captured by U.S. forces in Iraq. But the talks never produced a deal.
In a sign the U.S. government is beginning to take action, the Treasury Department named Saad bin Laden and three other Al Qaeda operatives in new financial sanctions Friday. The department said it would seize any assets held by the operatives in U.S. jurisdictions, and described Bin Laden as someone who had "made key decisions for Al Qaeda."
Iran's nuclear ambitions have been a major source of friction with the United States and other Western countries. In his farewell session with reporters, McConnell said he believed that Iran was pursuing a nuclear weapon.
McConnell is expected to be replaced in coming weeks by retired Navy Adm. Dennis C. Blair, who has been nominated by Obama.