IRAN: US intelligence officials, already focused on Iran's potential for building nuclear weapons, are struggling to solve a more immediate mystery: the murky relationship between the new Tehran leadership and the contingent of al-Qaeda leaders living in the country.
Some officials, citing evidence from highly-classified satellite feeds and electronic eavesdropping, believe that the Iranian regime is hosting much of al-Qaeda's remaining brains trust and allowing the senior operatives freedom to communicate and help plan their operations.
They suggest that new president Mahmoud Ahmadinejad may be forging an alliance with al-Qaeda operatives to expand Iran's influence or, at a minimum, that he is looking the other way as al-Qaeda leaders in Iran collaborate with their counterparts elsewhere.
"Iran is becoming more and more radicalised and more willing to turn a blind eye to the al-Qaeda presence there," said one US counterterrorism official.
The accusations from US officials about Iranian nuclear ambitions and ties to al-Qaeda echo charges that administration figures made about Iraq in the run-up to the US invasion three years ago.
Those charges about Iraq have been largely discredited, and in the case of Iran, some intelligence officials and analysts are unconvinced. If anything, they suggest, escalating tensions between Shias and Sunni Arabs in Iraq would logically cause Iran's Shia government to crack down on al-Qaeda, whose Sunni leadership has denounced Shias as infidels.
A US intelligence official says he does not see any relaxation in Iranian restrictions on al-Qaeda members. "I'm not getting the sense that these people are free to roam, free to plot," the official said. But even that official conceded that the relationship between Tehran and al-Qaeda officials within Iran is largely unknown to US and allied intelligence, especially since Mr Ahmadinejad's election last summer.
To some US intelligence officials, what they don't know is the most worrisome of all. "I don't need to exaggerate the difficulty in determining what these people are up to at any given moment," said one. The US counterterrorism official was more blunt. "We don't have any intelligence going on in Iran, no people on the ground."
US, European and Arab intelligence officials spoke on condition of anonymity because they are not authorised to discuss such matters publicly.
Ties between Iran and al-Qaeda were highlighted by the September 11th commission, which disclosed a wealth of detail about such connections in its final report.
The commission said Iran and al-Qaeda had worked together sporadically throughout the 1990s, trading secrets, including how to make explosives.
Iranian representatives to the UN did not return repeated calls seeking comment. Three months ago, Iran said there were no more al-Qaeda members in the country. US officials reject that claim.
In Tehran, analysts said US officials are misreading Iran's intentions. That the Iranian government has not turned over al- Qaeda suspects to the US should be no surprise, given the state of relations between the two countries, said Nasser Hadian, a political analyst at Tehran University.
"They won't. Why should they [ without receiving something in return]?," he asked. "Unfortunately, now everything is becoming commercialised, if I may use that term.
"Everything is being assessed on its value in negotiations, and that is on both sides."
Some of the al-Qaeda members have been indicted in the US for terrorist attacks, but Iran has refused to extradite them.
Among them is Saif al-Adel, believed to be one of the highest-ranking members of al-Qaeda's hierarchy, behind Osama bin Laden, and his deputy, Ayman al-Zawahri.
Whatever restrictions might be placed on al-Qaeda activities within Iran, al-Adel was able last year to post a lengthy dispatch about al-Qaeda activities in Iran and Iraq that was widely circulated on the internet. US intelligence officials believe the posting was authentic.
In that, al-Adel said he had used hideouts in Iran to plot with Abu Musab al-Zarqawi to make Iraq the new battleground in the group's war against the US. Iran had detained many of al-Zarqawi's men, al- Adel wrote, but they ultimately slipped into Iraq and began attacking US forces.
For several years, the US counterterrorism official said, satellite feeds have helped officials monitor some day-to-day activities and movements of al-Adel and other senior al-Qaeda operatives in Iran. Intelligence suggests that the al-Qaeda leaders have been monitored by Iranian authorities but could move and communicate somewhat.
US officials also said other senior al- Qaeda figures - including al-Zarqawi, now the group's 'point' man in Iraq - have moved in and out of Iran with the possible knowledge or complicity of Iranian officials. The al-Qaeda members in Iran include three of Osama bin Laden's sons, including two who are considered his heirs apparent - Saad and Hamza.