Akiko Saberi says she is concerned about her daughter's health
Iran's president says Iranian-US journalist Roxana Saberi must have the legal right to defend herself in an appeal against her spying conviction.
The request came in a letter from his office to Tehran's prosecutor, state media reported, a day after Ms Saberi was jailed for eight years.
Our Tehran correspondent says it is an unusual intervention by Mr Ahmadinejad.
US President Barack Obama has expressed concern at the 31-year-old's sentencing after a secret one-day trial in Tehran.
Mr Obama urged Tehran to free Ms Saberi, saying he was "deeply concerned" for her safety, and adding that the US would contact Iran about the case through Swiss intermediaries.
"I have complete confidence that she was not engaging in any sort of espionage," he told reporters in Trinidad where he attended a regional summit.
Roxana Saberi, who was arrested in January and went on trial this week, denies the charge and plans to go on hunger strike, her father Reza has said.
Her lawyer has said he will lodge an appeal.
Ms Saberi's mother Akiko expressed concern for her daughter's health, saying she was "very, very frail."
She said it was hard to believe how a country could treat a human being like this.
Mr Ahmadinejad said the rights of Ms Saberi and jailed Iranian-Canadian blogger Hossein Derakhshan, who has been behind bars since November, must not be violated in any way.
Barack Obama says Roxana Saberi should be released
"Please take the necessary measures to ensure that the process of examining the charges against the aforementioned individuals are being carried out carefully and fairness, justice and regulations are observed," he wrote in the letter to prosecutors.
"Please, personally observe the process to ensure that the defendants are allowed all legal rights and freedom in defending themselves and that their rights are not violated even by one iota," reported Iranian official government news agency Irna.
The verdict came despite calls by the Obama administration for Ms Saberi's release and diplomatic overtures to Iran after three decades of severed ties.
It raises suspicions over whether the case has been hijacked by hardliners within the Iranian government, eager to sabotage any reconciliation, the BBC's Jon Leyne reports from Tehran.
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