Iran has rejected US demands to hand over several suspected al-Qaeda members it has detained.
Al-Qaeda spokesman Sulaiman Abu Ghaith is alleged to be in Iran
A foreign ministry spokesman said the suspects had committed offences in Iran and would be tried in its courts, Iranian media reported.
On Monday, the Americans called on Iran to hand over all al-Qaeda suspects to the US or to the countries of their origin.
In June, Iran said it was holding several al-Qaeda members, with reports suggesting some were senior figures.
US officials have long alleged that some of al-Qaeda's more senior members have sought sanctuary in Iran and have repeatedly accused Tehran of harbouring them.
Iran has strenuously denied such allegations, although it admits that some may have slipped through its borders.
US officials have also said they believe the suicide bombings in the Saudi capital, Riyadh, in May were planned by al-Qaeda operatives in Iran - again a charge denied by Iran.
Among those possibly in Iranian detention are al-Qaeda spokesman Sulaiman Abu Ghaith and Osama Bin Laden's son, Saad Bin Laden.
Osama Bin Laden's security chief Saif al-Adel, sometimes regarded as al-Qaeda's current number three leader and alleged to have trained some of the 11 September hijackers, is also said to be in the country.