WASHINGTON (Reuters) - Iranian authorities have denied the appeal of a Princeton University student who had been convicted on espionage charges and sentenced to 10 years in prison, the university and his wife said on Thursday.

Xiyue Wang, a naturalized American citizen from China, arrested in Iran last August while researching Persian history for his doctoral thesis at Princeton University, is shown with his wife and son in this family photo released in Princeton, New Jersey, U.S. on July 18, 2017. Courtesy Wang Family photo via Princeton University/Handout via REUTERS

Xiyue Wang, a history doctoral student and U.S. citizen who was conducting dissertation research in Iran in 2016 when he was detained by Iranian authorities, was accused by Iran of “spying under the cover of research,” a claim his family and university deny.

“Iranian authorities have denied Xiyue Wang’s appeal of his conviction and 10-year prison sentence for espionage that he did not attempt or commit,” Princeton University said in a statement. “We are distressed that his appeal was denied, and that he remains unjustly imprisoned.”

It was not immediately clear when exactly Wang’s appeal was denied. News of his detention in Iran and his 10-year sentence first came in mid-July.

“I am devastated that my husband’s appeal has been denied, and that he continues to be unjustly imprisoned in Iran on groundless accusations of espionage and collaboration with a hostile government against the Iranian state,” Wang’s wife, Hua Qu, said in a statement on Princeton’s website. “Our young son and I have not seen Xiyue in more than a year, and we miss him very much.”

Iran had said Wang was an American spy.

Qu said she worries about Wang’s health and well-being while he is in prison.

“We hope the Iranian officials can release him immediately so he can resume his studies at home and so that our family will be together again,” she said.

A spokesman for Iran’s mission to the United Nations did not immediately respond to a request for comment.

A State Department official declined to offer specific information on Wang’s case, citing privacy concerns.

“We call for the immediate release of all U.S. citizens unjustly detained in Iran so they can return to their families,” the official said.

President Donald Trump has taken a hard line against Iran and his administration has vowed to counter what it sees as Iran’s destabilizing policies in the Middle East.

Last month, the White House said Trump “is prepared to impose new and serious consequences on Iran unless all unjustly imprisoned American citizens are released and returned,” though it did not specify what those consequences might be.