Iran confirmed Wednesday it is holding U.S. Navy veteran Michael R. White at a prison in the country, making him the first American known to be detained under President Donald Trump's administration.

White's detention adds new pressure to the rising tension between Iran and the U.S., which under Trump has pursued a maximalist campaign against Tehran that includes pulling out of its nuclear deal with world powers.

Although the circumstances of White's detention remain unclear, Iran in the past has used its detention of Westerners and dual nationals as leverage in negotiations.

The semi-official Tasnim news agency, believed to be close to the country's paramilitary Revolutionary Guard, reported the confirmation, citing Foreign Ministry spokesman Bahram Ghasemi.

"An American citizen was arrested in the city of Mashhad some time ago and his case was conveyed to the U.S administration on the first days" of his incarceration, Ghasemi was quoted as saying.

The New York Times has quoted White's mother saying she learned three weeks ago that her son is alive and being held at an Iranian prison. His arrest was first reported by IranWire, an online news service run by one-time Iran detainee Maziar Bahari, which interviewed a former Iranian prisoner who said he met White at Vakilabad Prison in Mashhad in October. Mashhad is about 95 kilometers (60 miles) east of Tehran, Iran's capital.  

Ghasemi also denied any mistreatment of prisoners in Mashhad, as alleged by the former prisoner quoted in the IranWire story. He described the allegations as "psychological warfare."

The Associated Press has been unable to reach members of White's family. The State Department said it was aware of reports of an American citizen's arrest, but was otherwise unable to comment.

White's mother, Joanne White, had told the Times that her 46-year-old son, who lives in Imperial Beach, California, went to Iran to see his girlfriend and had booked a July 27 flight back home to San Diego via the United Arab Emirates. She filed a missing person report with the State Department after he did not board the flight. She added that he had been undergoing treatment for a neck tumor and has asthma.

While relations between Iran and the U.S. warmed under President Barack Obama, they've turned increasingly toxic under Trump. Trump in May withdrew America from the nuclear deal, which saw Iran limit its enrichment of uranium in exchange for the easing of economic sanctions.

Trump has said he withdrew from the deal to put further pressure on Iran over its ballistic missile program, as well as to blunt its influence in the wider Mideast. While American officials deny that the goal of the U.S. policy is regime change, his administration includes officials who have openly called for Iran's government to be overthrown.

The worsening ties could be heard in remarks Wednesday by Iran's supreme leader, Ayatollah Ali Khamenei, who previously has told Trump he "cannot do a damn thing" to stop Iran.

"Some U.S. officials pretend that they are mad," Khamenei said. "Of course I don't agree with that, but they are first-class idiots."

There are four other known American citizens being held in Iran.

Iranian-American Siamak Namazi and his 82-year-old father Baquer, a former UNICEF representative who served as governor of Iran's oil-rich Khuzestan province under the U.S.-backed shah, are both serving 10-year sentences on espionage charges. Iranian-American art dealer Karan Vafadari and his Iranian wife, Afarin Neyssari, received 27-year and 16-year prison sentences, respectively. Chinese-American graduate student Xiyue Wang was sentenced to 10 years in prison for allegedly "infiltrating" the country while doing doctoral research on Iran's Qajar dynasty.

Iranian-American Robin Shahini was released on bail in 2017 after staging a hunger strike while serving an 18-year prison sentence for "collaboration with a hostile government." Shahini is believed to still be in Iran.

Also in an Iranian prison is Nizar Zakka, a U.S. permanent resident from Lebanon who advocated for internet freedom and has done work for the U.S. government. He was sentenced to 10 years on espionage-related charges.

Former FBI agent Robert Levinson, who vanished in Iran in 2007 while on an unauthorized CIA mission, remains missing as well. Iran says that Levinson is not in the country and that it has no further information about him, though his family holds Tehran responsible for his disappearance. Tehran now says it has no information about him.

Others held with Western ties include Nazanin Zaghari-Ratcliffe, a British-Iranian woman who is serving a five-year prison sentence for allegedly planning the "soft toppling" of Iran's government while traveling with her young daughter. As pressure mounts in Britain for her release, Iranian state television this week aired footage of her arrest at Tehran's Imam Khomeini International Airport.

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Gambrell reported from Dubai, United Arab Emirates.