WASHINGTON – A U.S. Navy veteran was sentenced to 10 years in an Iranian prison, according to his attorney, potentially fueling more friction between the United States and Iran.

Michael T. White, a veteran from California who has been held in the country since July, was given a decade behind bars, according to his attorney Mark Zaid, who added he is still unsure of the details that led to charges against White.

"We are just learning of information concerning Michael's sentence. After receiving news of the conviction we're in the process of hiring a local Iranian attorney to pursue whatever appeals exist," Zaid said. "It's unclear at this time whether Michael is simply an unfortunate foreigner caught in a very different legal system or being used as a political pawn."

The Associated Press and New York Times reported White was charged with insulting Iran's supreme leader, Ayatollah Ali Khamenei, and posting private information online.

The State Department said it was aware of White's detention but had no additional information. "We have no higher priority than the safety and security of U.S. citizens abroad," a State Department official said in a statement.

White was arrested in July after reportedly going to the country to visit his girlfriend. He was the first American detained in Iran during the Trump presidency.

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His long sentence in an Iranian prison sets up what could be another flashpoint in a longstanding diplomatic standoff between Iran and the U.S. over detainees and hostages.

Disputes between the two countries stretch back to Iran's Revolution in 1979 when 52 American diplomats and citizens were held hostage inside the U.S. Embassy in Tehran for 444 days from November 4, 1979, to January 20, 1981.

Relations between the United States and Iran are already strained. Last year, President Donald Trump pulled out of the Iran nuclear deal, in which the U.S. and allies eased sanctions on Tehran as it gave up the means to make nuclear weapons. Since then, Trump has beefed up sanctions against the country and accused Iran of secretly working toward the goal of building nuclear weapons.

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Iran's foreign ministry has not released much about White's case besides that White has been held since July. Gholamali Sadeghi, an Iranian prosecutor, said in January that White was being held in connection to a "private complaint," according to the semi-official Mehr news agency.

"He is not in a good physical and mental condition," Ivar Farhadi, an Iranian who says he was held in the same prison as White before his own release in November, told USA TODAY earlier this year. Farhadi fled to Turkey, from where he relayed his encounter with the American. "If the U.S. government does not push for his freedom, the possibility of him surviving is very poor," he said in a private exchange via Twitter.

Farhadi said White is being held inside the Vakilabad Prison in the eastern city of Mashhad. He described conditions there as akin to torture. "It is filled with dangerous criminals, always cold, and cameras everywhere. The lights were always on," he said.

At least three other U.S. citizens are also being held in Iranian prisons under espionage charges the State Department has denounced as “fabricated.” Chinese-American Xiyue Wang as well as Iranian-American businessman Siamak Namazi and his father, Baquer Namazi, are all serving 10-year sentences.

Contributing: Kim Hjelmgaard, Deirdre Shesgreen and David Jackson