Reza Saberi said the court asked him questions about a hunger strike that his daughter, Roxana Saberi, started after being sentenced last week to eight years in prison. That sentence followed a closed one-day trial for Saberi, a 32-year-old journalist from North Dakota who has been living in Iran since 2003.
She started the hunger strike to protest her imprisonment, he said.
On Wednesday, her father told a judge that his daughter looked thinner than when he last saw her and that she had lost about 10 pounds.
A Tehran judge, meanwhile, told Iran's state-run media that the hunger strike was not real.
Reza Saberi has said his daughter started the hunger strike Tuesday.
"She says she will continue the strike until she is free from prison," he said.
Reza Saberi said he spoke to his daughter in a one-minute call, and "she did not give us the chance to tell her not to do it."
The sentence prompted sharp denunciations from U.S. President Barack Obama, as well as other U.S. and international officials.
Saberi's legal team has said it will appeal her conviction. Judiciary Chief Ayatollah Hashemi Shahroudi has ordered the head of Tehran's Justice Department to make sure the appeals process is quick and fair.
Iranian officials initially said Saberi was held for buying a bottle of wine. The Foreign Ministry later said she was detained for reporting without proper credentials.
Saberi has been living in Iran since 2003, said the Committee to Protect Journalists, a journalists' advocacy group.
She has freelanced for National Public Radio and other news organizations, and was writing a book about Iranian culture.
Iranian authorities revoked her press credentials in 2006, but Saberi continued to file short news items without permission, the journalists' group said.
Saberi was detained in January, although no formal charges were disclosed. On April 9, word emerged that Saberi had been charged with espionage.
"Without press credentials and under the name of being a reporter, she was carrying out espionage activities," Hassan Haddad, a deputy public prosecutor, told the Iranian Students News Agency.
Authorities also said Saberi had confessed. Her father said he thinks she was coerced into making damaging statements.
Shirin Ebadi, an Iranian human-rights activist, has joined Saberi's legal team. Ebadi won a Nobel Peace Prize in 2003.
