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An American journalist jailed by Iran on charges of spying for the United States "is in bad condition," her father said Monday, almost a week after she went on hunger strike.

Reza Saberi said he and his wife Akiko visited their daughter Roxana in Tehran's Evin jail on Sunday, taking flowers for her 32nd birthday.

"She is very, very weak and frail ... she is in a bad condition. She can hardly stand up," he told Reuters. "I'm worried about her health. I'm worried about her life."

The 68-year-old said he pleaded with her to stop the hunger strike, but she resisted during the 20-minute visit.

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Roxana Saberi, a dual American-Iranian citizen, was convicted more than a week ago and sentenced to eight years in prison after a swift, one-day trial behind closed doors. She began her hunger strike Tuesday to protest her imprisonment, her father said.

"She said that she has started a hunger strike and this is the fifth day and that she will continue until she is free. I tried to tell her that this can be dangerous, but she didn't give me any time to protest," her father, Reza Saberi, told The Associated Press.

The case has been a source of tension between the United States and Iran at a time when the Obama administration has said it wants to engage its longtime adversary. The U.S. has called the accusations against Saberi baseless and demanded her release.

Saberi's father said her lawyer appealed the court's ruling on Saturday — less than a week after Iran's judiciary spokesman said an Iranian appeals court would reconsider her verdict, an indication her sentence could be commuted.

Iran's judiciary chief has ordered a full investigation into the case, and President Mahmoud Ahmadinejad has urged Tehran's chief prosecutor to ensure Saberi be allowed a full defense during her appeal.

Saberi was arrested in late January and initially accused of working without press credentials. But earlier this month, an Iranian judge leveled the far more serious allegation of espionage.

Saberi, who was born in the United States and grew up in Fargo, North Dakota, moved to Iran six years ago and worked as a freelance journalist for news organizations including National Public Radio and the British Broadcasting Corp. She received Iranian citizenship because her father was born in Iran.

Saberi's parents have traveled to Iran from their home in Fargo in a bid to help win their daughter's release. Her father has said his daughter, who was Miss North Dakota in 1997, had been working on a book about the culture and people of Iran, and hoped to finish it and return to the United States this year.

Reza Saberi said he hoped to see his daughter in prison on Monday and was concerned about her health.

"After five days, I am pretty certain that she must be very weak now, because we know she is already frail," he said.

Iran has released few details about the charges against Saberi, but Iran's Intelligence Minister Gholam Hossein Mohseni Ejehi has said that the initial investigation of Saberi was done by an expert on security and counterespionage at the Intelligence Ministry before her case was referred to the court.

On Monday, Iran's Foreign Ministry spokesman said Saberi's supporters would be surprised if the judiciary made the evidence against her public.

"Should the judge decide to expose details, the revelations will definitely make some of her supporters inside and outside Iran think seriously about the case," Hasan Qashqavi told a press conference. He didn't elaborate or say what the evidence was against Saberi.

He warned the U.S. not to make judgments or interfere with the case and stressed that Saberi was tried as an Iranian citizen.

"Saberi is treated as an Iranian national because all her documents including her passport and identification papers prove her Iranian identity. ... Her case has nothing to do with a foreign party," he said in a reference to the United States.

An Iranian investigative judge involved in the case also alleged that Saberi was passing classified information to U.S. intelligence services.

The U.S. broke off diplomatic relations with Iran after the 1979 Islamic revolution and the takeover of the U.S. Embassy in Tehran by hard-line Iranian students. The Obama administration has said it is working with Swiss intermediaries who represent U.S. interests in Iran to secure her release.

The Associated Press and Reuters contributed to this report.