White, a cancer survivor, has 22 days to appeal the court's actions, Zaid said.
White's family has become increasingly worried about his health and has been scrambling to raise money to hire a lawyer in Iran to represent him and gain more clarity about the charges of which he was convicted.
In addition to concerns that his cancer might re-emerge, White's family said that he suffers from asthma and that his immune system has been compromised by chemotherapy treatments.
White was detained in Mashhad after plainclothes police pulled over a taxi he was riding in around July 22, shortly before he was scheduled to return to the United States, his family says.
Several months went by before White's family learned of his whereabouts.
In February, the family said it was informed by Iranian authorities that White did not face espionage charges and that his arrest was linked to a "private complaint."
But on Monday, Mashhad's prosecutor, Gholamali Sadeghi, announced that White was convicted of crimes related to national security issues.
"None of the crimes he was convicted of are related to national security issues," Zaid said Thursday. "And White is being held separate from political prisoners."
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In recent years, hard-liners in Iran's judiciary and security apparatus have increasingly targeted Iranian dual citizens and Western nationals whom they accuse of attempting to "infiltrate" the Islamic Republic. Members of Iran's Islamic Revolutionary Guard Corps have typically used these individuals as bargaining chips for future negotiations.
As of January, White was the eighth known foreigner with U.S. citizenship or permanent residency status held in Iran, according to the New York-based nonprofit Center for Human Rights in Iran.
Although Trump had said freeing Americans held overseas "is a priority" in his administration, worsening relations with Iran make negotiating their release much more difficult.
Last year Trump withdrew from the landmark nuclear deal that sought to restrict Iran's nuclear activities and imposed tough economic sanctions.
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