Even before its official release today, the final report by the commission investigating the Sept. 11, 2001, attacks reignited the political debate over Iraq and whether al Qaeda had a significant relationship with Saddam Hussein, as President Bush and other administration officials have alleged over the past two years.

The report, to be released at a Washington news conference this morning, echoes earlier findings by the Sept. 11 commission's staff that Iraq and al Qaeda had no "collaborative relationship" and dismisses as unfounded reports of a meeting between an Iraqi intelligence officer and Sept. 11 ringleader Mohamed Atta, said officials familiar with the document.

On Iran, by contrast, the report concludes that al Qaeda's relationship with Tehran and its client, the Hezbollah militant group, was long-standing and included cooperation on operations, the officials said. It also details previously unknown links between the two, including the revelation that as many as 10 of the Sept. 11 hijackers may have passed through Iran in late 2000 and early 2001 because Iranian border guards were instructed to let al Qaeda associates travel freely, sources familiar with the report have said.

Commission and government officials emphasize that they have found no indication that Tehran knowingly helped in the plot. But the commission report will cite evidence that Iran allowed al Qaeda members into the country even after the attacks.

The Sept. 11 panel has also raised the possibility that al Qaeda may have had a "yet unproven" role in the 1996 Khobar Towers bombing, which killed 19 U.S. servicemen and has been blamed on a Saudi Hezbollah group. Iran is a primary sponsor of Hezbollah, or Party of God, which the United States considers a terrorist group.

Many of the commission's findings about Iran were discovered only in recent weeks from, among other sources, electronic intercepts and interrogations of al Qaeda suspects in U.S. custody, sources familiar with the commission's findings said. Even before then, Chairman Thomas H. Kean (R), a former New Jersey governor, said, "There were a lot more active contacts, frankly, with Iran and with Pakistan than there were with Iraq."

Al Qaeda's ties to Iraq are sketchier. At the leadership level, Osama bin Laden and his associates for years saw Hussein as one of the secular Muslim leaders who had to be replaced. On the other side, as the Senate Select Committee on Intelligence recently reported, Hussein dealt harshly with Islamic extremists, and the CIA had intelligence reports that "the regime sought to prevent Iraqi youth from joining al Qaeda."

The Sept. 11 commission was the first to disclose that bin Laden at one time sponsored Ansar al-Islam, an anti-Hussein, Sunni Kurdish group in northern Iraq, but the al Qaeda leader dropped that aid at the request of the Sudanese. At that time, the Sudanese were providing bin Laden with haven and the Khartoum government wanted good relations with Iraq.

Although an Iraqi intelligence official may have met with bin Laden in Sudan in 1994, after two failed attempts, the CIA told the panel, nothing apparently developed from the meeting. The Senate report also cautioned that one source for the 1994 meeting was an Italian newspaper article published four years later and that other information came from "raw reports from foreign sources."

Two senior bin Laden lieutenants now in CIA custody, Abu Zubaida and Khalid Sheik Mohammed, both insisted that al Qaeda cooperation with Iraq would have been difficult. Abu Zubaida, according to the Senate report, told CIA interrogators that joint activities were "extremely unlikely," although he admitted it was possible there were communications he did not know about.

The Sept. 11 commission raised questions about whether al Qaeda was behind the 1993 World Trade Center attack and challenged Vice President Cheney's repeated assertion that Iraq may have been connected through one of the plotters.

The CIA considers Ramzi Yousef, ringleader of the 1993 bombing, to have been an independent operator, although he trained in Afghanistan and subsequently trained al Qaeda recruits. His entry into the United States on a phony Iraqi passport before carrying out the bombing is no indication Iraq was involved in the plot because stolen Iraqi passports "were common at this time," a CIA report said.

The vice president has repeatedly pointed to Abdul Rahman Yasin, a fugitive from the 1993 Trade Center prosecution, because he fled to Iraq with Iraqi assistance. But CIA officials told the Senate panel that Yasin, an Iraqi, was held "in custody since that time" in Baghdad by Iraqis who explained they feared the United States would misrepresent his role. Yasin, however, disappeared after the U.S. invasion.

The Sept. 11 commission also adopted the position of the FBI and the CIA that there is no evidence to support allegations, again repeated by Cheney, that Atta met Ahmed Khalil Ibrahim Samir al-Ani, the Iraqi Intelligence Service chief, in Prague, in the spring of 2001. A surveillance camera and cell phone records place him in Florida and Virginia during that time. Photographs of another alleged meeting between Atta and al-Ani in October 1999 were also analyzed by CIA and found inconclusive. Intelligence at that time placed Atta in Egypt, visiting his family.