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Iran seized a Navy veteran from California five months ago while he was visiting the country and is still holding him on unspecified charges, his family said Tuesday.

Michael R. White was captured by authorities in late July, when he was there to visit his Iranian girlfriend, the veteran’s mom, Joanne White, told NBC News.

White’s detention is bound to aggravate tensions between the two countries, which have soared since President Donald Trump withdrew the U.S. from an international nuclear agreement with Iran and reimposed punishing economic sanctions.

The State Department is “aware of reports” of White’s detention but declined further comment, officials said. It was not immediately known how long White had been out of the Navy.

Joanne White said she didn’t want to discuss her son’s detention in detail for fear of putting him in any more danger.

“I don’t want to say anything else at this time,” she said.

Michael R. White, a U.S. Navy Veteran, was detained in Iran on unspecified charges in July 2018. Courtesy of Joanne White

White, 46, is from Imperial Beach, in the farthest southwest corner of San Diego County and the continental United States.

In 2014, White reached out to the American Rogues, a Celtic band dedicated to raising money for veterans, to ask for their help in raising $5,000 so he could help a woman suffering from lupus in the Middle East. It's not clear if the girlfriend White was visiting last year is this same woman from 2014.

"He said he was hoping to bring her to the U.S. He also stated he planned on repaying all donors," vocalist and band leader Nelson Stewart told NBC News in an email on Tuesday.

"I discussed the matter with my friends and advisers and we agreed that the proposal didn't fit the mandate of the band, which is to assist veterans directly. I wished Michael the best of luck and we never heard from him again."

Iran is holding at least four other Americans: Morad Tahbaz, an Iranian-American businessman and environmentalist: Xiyue Wang, a Princeton graduate student; and two U.S. citizens of Iranian descent, business consultant Siamak Namazi, and his 82-year-old father, Baquer Namazi, a former UNICEF official.

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Tahbaz has been held since January 2018. Wang has been imprisoned since August 2016. Siamak Namazi has been held since October 2015, and his father was first detained in February 2016. The Namazis have been sentenced to 10 years in prison on espionage charges that a U.N. panel and human rights groups say are groundless.

“They’re feeling extremely abandoned and hopeless,” Babak Namazi, the son of Baquer Namazi, told NBC Nightly News.

Babak Namazi, who is based in Dubai, said his elderly father’s health is deteriorating, and he fears he will die in custody.

“It's really necessary for the U.S. government to find a solution and find a way to get the Americans back home quickly and safely before it's too late,” he said.

But the Trump administration has so far chosen not to enter into a dialogue with Iran on the detained Americans, despite repeated appeals from families of those held in Iran.

A number of family members accuse the Trump White House of failing to make the Americans imprisoned in Iran a high-enough priority, despite the president’s campaign promise. They also say the White House has assigned too many officials as the lead contact for their cases over the past two years, NBC News reported in December.

Secretary of State Mike Pompeo, who was in Jordan on Tuesday as part of an eight-nation tour of the Middle East, vowed to inflict more economic and political pain on Tehran over its “malign” role in the region.

“We are redoubling not only our diplomatic but our commercial efforts to put real pressure on Iran,” Pompeo said.

Iran’s U.N. mission did not respond to requests for comment.

The United States hasn’t had diplomatic relations with the country since the overthrow of the shah in 1979. The Swiss government has acted as the intermediary for any talks between Washington and Tehran.

Michael White's mother told The New York Times, “All I know is that he is alive and they were putting in a request for a consular visit by the Swiss.” She added that her son had been supposed to return from Iran on a flight through Dubai.

White's detainment was first reported by Iranwire, an online news operation operated by Iranian expatriates, before it was picked up by The New York Times on Monday.

The Iranwire report was based on the account of a former Iranian prisoner who allegedly met White while they were both at Vakilabad Prison in the city of Mashhad in October, according to the Times.

White has been undergoing chemotherapy and radiation treatment for a neck tumor, his family said. He also suffers from acute asthma, according to his mother.

He has been to Iran "five or six times" to visit his girlfriend there, Joanne White said.

White’s brother, Steve White, told NBC7 San Diego that his family is deeply worried about him.

“Thinking of what he might be going through, it’s heartbreaking, absolutely heartbreaking,” the brother said in a phone interview with NBC7 San Diego.

“We’re all very scared and worried,” Steve White said. “We’re praying for him and we’re praying for him to come home by his birthday,” which he said is later this month. “We’re hoping.”

David K. Li and Jon Sanders reported from New York, Daniel DeLuce from Washington D.C., Caroline Radnofsky from London, and Bridget Naso from San Diego.