Last week, the CIA sent an urgent report to President Bush's National Security Council: Iranian authorities had arrested two al-Qaeda operatives traveling through Iran on their way from Pakistan to Iraq. The suspects were caught along a well-worn, if little-noticed, route for militants determined to fight U.S. troops on Iraqi soil, according to a senior intelligence official.

The arrests were presented to Bush's senior policy advisers as evidence that Iran appears committed to stopping al-Qaeda foot traffic across its borders, the intelligence official said. That assessment comes at a time when the Bush administration, in an effort to push for further U.N. sanctions on the Islamic republic, is preparing to publicly accuse Tehran of cooperating with and harboring al-Qaeda suspects.

The strategy has sparked a growing debate within the administration and the intelligence community, according to U.S. intelligence and government officials. One faction is pressing for more economic embargoes against Iran, including asset freezes and travel bans for the country's top leaders. But several senior intelligence and counterterrorism officials worry that a public push regarding the al-Qaeda suspects held in Iran could jeopardize U.S. intelligence-gathering and prompt the Iranians to free some of the most wanted individuals.

"There was real debate about all this," said one counterterrorism official. "If we go public, the Iranians could turn them loose." The official added: "At this point, we know where these guys are and at least they are off the streets. We could lose them for years if we go down this path."

The administration's planned diplomatic offensive is part of an effort to pressure Tehran from multiple directions. Bush has given the U.S. military the authority to kill or capture Iranian government agents working with Shiite militias inside Iraq. Yesterday, Defense Secretary Robert M. Gates said serial numbers and markings on some explosives used in Iraq indicate that the material came from Iran, but he offered no evidence.

With the aim of shaking Tehran's commitment to its nuclear program, Bush also approved last fall secret operations to target Iranian influence in southern Lebanon, in western Afghanistan, in the Palestinian territories and inside Iran. The new strategy, a senior administration official said, aims to portray Iran as a "terror-producing country, instead of an oil-producing country," with links to al-Qaeda, Hezbollah and death squads in Iraq.

U.S. officials have asserted for years that several dozen al-Qaeda fighters, including Osama bin Laden's son, slipped across the Afghan border into Iran as U.S. troops hunted for the perpetrators of the Sept. 11, 2001, attacks. U.S. and allied intelligence services, which have monitored the men's presence inside Iran, reported that Tehran was holding them under house arrest as bargaining chips for potential deals with Washington.

Last fall, Bush administration officials asked the CIA to compile a list of those suspects so the White House could publicize their presence. For years, the administration has not revealed their names, in part because it sought to protect its intelligence sources but also because at the time the U.S. government was concealing the identities of suspects it was holding in secret CIA custody.

But the names of some of the men in Iran have become public, including "high-value" targets such as al-Qaeda spokesman Sulaiman Abu Ghaith of Kuwait and Saif al-Adel of Egypt. U.S. intelligence officials said they are members of the "al-Qaeda operational management committee." U.S. intelligence officials said there are suspicions, but no proof, that one of them may have been involved from afar in planning an attack in Riyadh, Saudi Arabia, in May 2003. Intelligence officials said bin Laden's son Saad is also being held with the other men in Iran.

Five administration officials were made available for interviews for this story on the condition that they not be identified. Other officials who spoke without permission -- including senior officials, career analysts and policymakers -- said their standing with the White House would be at risk if they were quoted by name.

The State Department, Pentagon and CIA referred all questions about the story to the National Security Council. In a written response to questions, NSC spokesman Gordon Johndroe said: "Iran's sponsorship of terrorism is one of the reasons for the sanctions now against it. We note that U.N. Security Council resolutions already oblige all states to ensure that members of terrorist groups, including al-Qaeda, are brought to justice."

Since al-Qaeda fighters began streaming into Iran from Afghanistan in the winter of 2001, Tehran had turned over hundreds of people to U.S. allies and provided U.S. intelligence with the names, photographs and fingerprints of those it held in custody, according to senior U.S. intelligence and administration officials. In early 2003, it offered to hand over the remaining high-value targets directly to the United States if Washington would turn over a group of exiled Iranian militants hiding in Iraq.

Some of Bush's top advisers pushed for the trade, arguing that taking custody of bin Laden's son and the others would produce new leads on al-Qaeda. They were also willing to trade away the exiles -- members of a group on the State Department's terrorist list -- who had aligned with Saddam Hussein in an effort to overthrow the Iranian government.

Officials have said Bush ultimately rejected the exchange on the advice of Vice President Cheney and then-Defense Secretary Donald H. Rumsfeld, who argued that any engagement would legitimize Iran and other state sponsors of terrorism. Bush's National Security Council agreed to accept information from Iran on al-Qaeda but offer nothing in return, officials said.

But no information has been forthcoming, intelligence officials said. One official said the CIA and the Pentagon's Defense Intelligence Agency have disagreed over how effectively the Iranians are controlling al-Qaeda members and whether the Tehran government is aware of the extent of al-Qaeda movements through the country.

Nevertheless, administration officials said they are determined to press Iran on the matter.

"We are not convinced that the Iranians have been honest or open about the level or degree of al-Qaeda presence in their midst," said one Bush adviser who was instrumental in coming up with a more confrontational U.S. approach to Iran. "They have not made proper accounting with respect to U.N. resolutions, have not been clear about who is in detention and have not been clear as to what is happening to individuals who might be in custody."

Bush administration officials pointed to U.N. Security Council Resolutions 1267 and 1373, which state that harboring al-Qaeda members constitutes a threat to international peace and security, and authorize force to combat that threat. The resolutions compel nations to share any information on al-Qaeda suspects and give the United Nations authority to freeze the assets of suspects and those who provide them with safe haven.

Two U.S. officials said the administration plans to argue that Iran is violating those resolutions. A team of senior U.S. officials has been holding briefings for visiting European diplomats on the issue while administration lawyers prepare options for holding Iran in violation of U.N. resolutions.

"We've started a more aggressive and major attempt to try to convince other countries to use their influence on this issue," a senior U.S. diplomat said. "Until now, the Europeans have been focused on the nuclear issue and we want this high up on the agenda."

But another government official predicted that no European country would support a call on Iran to turn the al-Qaeda group over to U.S. military detention at Guantanamo Bay, Cuba, a facility widely condemned by Washington's closest allies. In the past year, U.S. officials said they successfully pushed Egypt, Kuwait and Saudi Arabia to seek extradition of their citizens held in Iran, but Tehran rebuffed the requests. Administration officials said they interpreted the refusal as evidence of cooperation between the Iranian government and the group.

"We'd be happy to see them face trial anywhere," a senior administration official said.

Staff researcher Julie Tate contributed to this report.