The Iranian frontier with Afghanistan is a wild and desolate area of goat farmers and mud-brick huts, the perfect place for illicit opium--and terrorists--to cross the border. But the region is hardly a no man's land. U.S. intelligence believes that in faraway Tehran, the hard-line Islamist clerics who now exercise near total control over Iran directed their border guards to help jihadists coming from Afghanistan. And sometime between October 2000 and February 2001, according to the forthcoming final report of the 9-11 Commission, eight to 10 of the "muscle" hijackers of the September 11 plot were among those who benefited from this Iranian good-fellowship.

That conclusion--the strongest evidence yet of a relationship between Iran and Al Qaeda--is one of the most surprising findings to emerge in the commission's report, which is due out this week. According to a December 2001 memo buried in the files of the National Security Agency, obtained by the commission, Iranian officials instructed their border inspectors not to place Iranian or Afghan stamps in the passports of Saudi terrorists traveling from Osama bin Laden's training camps through Iran. Such "clean" passports undoubtedly helped the 9/11 terrorists pass into the United States without raising alarms among U.S. Customs and visa officials, sources familiar with the report told NEWSWEEK.

The 9-11 Commission report emphasizes there is no evidence suggesting that Iranian officials had advance knowledge of the September 11 plot. Still, the report raises new, sharper questions about whether the Bush administration was focused on the right enemy when it decided to remove Saddam Hussein. The NSA memo adds to a large accumulation of intelligence indicating that Iran has had more suspicious ties to Al Qaeda than Iraq did. Among those who once had a base in Iran: Abu Mussab al-Zarqawi, allegedly the No. 1 terrorist in Iraq today. Meanwhile the commission found there was no "collaborative, operational" relationship between Iraq and Al Qaeda.

The 9-11 report will likely encourage some administration hawks who have long sought a harder U.S. line against Iran, the "Axis of Evil" member that has gotten the least attention. But Bush administration officials insist that the Iranian link to Al Qaeda was never clear. They also point to a change of attitude by Tehran since 9/11. Iranian officials claim they have "expelled or repatriated" large numbers of bin Laden followers, and last Saturday the country's intelligence chief, Ali Yunesi, announced new arrests. Yet other Qaeda suspects--like bin Laden's son Saad and Saif Al-Adel, once Al Qaeda's security chief, along with eight others--are believed to still be in Iran, possibly under some kind of protective custody to be used as leverage in future U.S.-Iran talks. According to separate intelligence reports, Qaeda suspects also continue to hide across the border from Afghanistan. "We just don't have good intelligence about what is going on in Iran," said one senior U.S. intelligence official. That's especially true since the Iraqi National Congress allegedly told Iranian officials after the Iraq invasion that U.S. intelligence was listening to their conversations. U.S. officials say that resulted in a devastating loss of monitoring capability.

All these unanswered questions make the 500-plus-page 9-11 Commission report--which was intended as a history of the September 11 plot--more relevant than ever to the future war on terror. Exhaustively researched, the report is described as "a thumping good read" and a blistering critique of the performance of the CIA, the FBI, the Federal Aviation Administration and a host of other agencies. To correct such failures, the report recommends the creation of a national-intelligence director who would serve as an "intelligence czar" with budgetary authority over the entire U.S. intelligence community. But some administration and intel officials are already deriding the plan as bureaucratic box-drawing.

The 9-11 report is destined to be picked apart by partisans seeking political ammunition against either the Clinton or Bush administrations. The report criticizes both for failing to respond to the bombing of the USS Cole off the coast of Yemen in October 2000, especially in light of multiple intelligence briefings strongly pointing to Qaeda complicity. Among the other new disclosures: Bill Clinton also got a strong warning that bin Laden wanted to hijack planes. On Dec. 4, 1998, Clinton was presented with a President's Daily Brief (PDB) with the eye-catching title "Bin Laden Preparing to Hijack U.S. Aircraft and other attacks," NEWSWEEK has learned. The PDB, which has just been declassified, was prompted by a British intelligence report that the son of the Egyptian "blind sheik" Omar Abdel-Rahman--who had been convicted of a plot to blow up New York City landmarks--proposed to hijack airplanes and ransom the passengers in exchange for his father's release. Clinton officials say they acted aggressively, placing New York City airports on maximum alert, but no evidence ever turned up establishing that the plot was real.

Curiously, the same information turned up 20 months later, in the Aug. 6, 2001, PDB presented to President George W. Bush, "Bin Laden Determined to Strike in U.S." One White House official suggested that the existence of the earlier PDB was evidence that President Bush was never properly informed by the outgoing Clintonites about the full depth of the Qaeda threat. "This was never briefed to us," said the official about the 1998 PDB. Clinton officials dismiss this, saying the timing of the declassification is likely an effort to blunt criticism that Bush bears primary responsibility for failing to avert 9/11.

Grimly, what the new 9-11 report makes clear is that nearly three years into the war on terror, America is still not close to understanding the enemy. And Washington seems less able to force Tehran to change its ways, especially since Bush has removed one of the chief threats to the mullah regime, Saddam Hussein, and is now bogged down in Iraq. As one intel official said before the Iraq war: "The Iranians are tickled by our focus on Iraq."

All these issues have gained new urgency as Bush officials warn of further attacks. Despite recent portrayals of bin Laden as a man hunted and on the run, U.S. counter-terrorism officials now say the threat today from Al Qaeda may be just as serious as in the summer of 2001. The warnings are based on unusually high-quality intelligence emanating from the Afghanistan-Pakistan border near Waziristan, where top Qaeda leaders are said to be hiding. "This is absolutely real," said one senior U.S. counterterrorism official. "We feel very confident that they are trying hard to attack us inside the United States before the election and that some of the operatives are already here." But just as with the 9/11 attacks, officials are at a loss to say what the actual plot is, who the plotters are, how they got here--and who helped them get here.