The comments by assistant attorney general Hossein Zebhi throw in doubt assurances he gave last week that juveniles offenders under the age of 18 faced a maximum sentence of life imprisonment and not execution.
Zebhi said in comments carried by Etemad Melli newspaper that Iran's attorney general and supreme court chief, who have to approve all death sentences, would commute the punishment in the case of convicted juvenile drug traffickers.
"An execution verdict for under-18 offenders is annulled in this manner," he said.
Juveniles committing murder could still face the gallows, however, Zebhi said, adding that whether the punishment was carried out would be up to families of victims.
"Qisas (retribution) is not a government punishment but a private one which the family of the victim are entitled to by law and Sharia (Islamic law)," he said, when questioned on whether murderers who committed their crimes before age 18 would face execution.
Under Iranian law, a murder victim's family has the right to pardon a convicted murderer by accepting blood money and leaving the convict to serve a prison sentence.
Some families have also been known to forgive a murderer without demanding compensation.
"The policy of the judiciary is to postpone qisas verdicts in order to obtain a pardoning from the family," Zehbi said.
Despite being a signatory to international child rights conventions, Iran executes juvenile offenders once they turn 18 and Amnesty International said six such offenders had been hanged this year.
Zebhi did not elaborate on the fate of juveniles convicted of other capital offences in the Islamic republic, including rape, armed robbery and adultery.
His comments last Wednesday that "life imprisonment is maximum punishment for offenders committing crimes under 18" had been welcomed by Amnesty and other rights advocates seeking to stop child executions.
Iran is a party to the International Covenant on Civil and Political Rights and the Convention on the Rights of the Child, whose signatories commit not to execute convicts who were under the age of 18 at the time of the offence.
Amnesty said Iran is the only country in the world known to have executed a juvenile offender in 2008.
The European Union and international human rights groups have sought to raise the age of legal responsibility in Iran's Islamic law, which deems a boy punishable from the age of 15 and a girl from the age of nine.
According to reports by the human rights group of Nobel peace laureate Shirin Ebadi, at least nine people were executed for crimes they committed as minors in the past Iranian year to March 2008, and 74 such offenders remain on death row.
On many occasions rights activists have sought to stop such executions by negotiating with the victims' families and by raising blood money, which is currently about 55,000 dollars for a man and half as much for a woman.
