The New York Times quoted a US official as saying Washington had approached Tehran with a request for the handover of members of Usama bin Ladin's network in Iranian custody, including Saif al-Adel, an Egyptian thought to be al-Qaida's security chief.
A senior US official told the newspaper that the Bush administration would reject any kind of swap for members of the Mujahideen Khalq, which is listed by the United States and the European Union as a “terrorist” organisation.
But since the ouster of Saddam Hussein Mujahideen Khalq members, the main armed opposition to Iran's Islamic government, are in camps in Iraq under US military supervision.
The Mujahideen joined the 1979 Islamic revolution that ousted the Shah but later broke ranks with Iran's new leaders.
There will be "no quid pro quo", the Times quoted the official as saying of the reported exchange proposal. The US has accused Iran of harbouring and assisting armed groups. Tehran denies the charge.
The New York Times quoted senior US and Middle Eastern officials as saying al-Adel was among al-Qaida members in Iranian custody after having been detained several weeks ago.
They said they believed other al-Qaida figures in Iranian hands include Sa'ad bin Ladin, one of Usama bin Ladin's older sons, and Sulayman Abu Ghaith, an al-Qaida spokesman.
"Many of them have been expelled but a large number of them are still in our custody - a mixture of big and small members"
The Times quoted a US official as saying Washington believes Iran is also holding Abu Masab al-Zarqawi, a Jordanian identified by the United States as a lieutenant of bin Ladin.
Iran publicly acknowledged for the first time last month that it was holding some senior al-Qaida figures.
"Since the collapse of the Taliban government we have arrested a large number of them," Intelligence Minister Ali Yunesi said on July 23. "Many of them have been expelled but a large number of them are still in our custody - a mixture of big and small members."