GENEVA (Reuters) - Iran confirmed on Wednesday it had arrested an American, confirming U.S. media reports about a case that risks further worsening relations with Washington.

The New York Times reported on Monday that Michael White, a 46-year-old U.S. Navy veteran, was arrested while visiting Iran and had been held since July on unspecified charges.

Iran had not confirmed the arrest before the state news agency IRNA carried a statement by foreign ministry spokesman Bahram Qassemi on Wednesday, which did not specify when it had happened or what crime he was accused of.

Qassemi said Iran had informed the U.S. government about White’s arrest within days of when he was taken into custody and denied that White had been poorly treated.

“These sorts of reports are lies and improper and are seriously rejected,” IRNA quoted Qassemi as saying.

White’s case is going through the legal process and officials will make a statement at the appropriate time, he added.

The case is likely to further worsen relations with the United States. President Donald Trump withdrew from an international agreement Iran’s nuclear program and re-imposed sanctions last year that hit the Iranian economy hard.

Several Americans have been detained in Iran in recent years and Trump warned in 2017 that Tehran would face “new and serious consequences” unless all unjustly held U.S. citizens were freed.

White’s mother, Joanne, told the New York Times her son had visited Iran “five or six times” to meet his Iranian girlfriend

She reported her son’s disappearance after he failed to return in July but learned from the State Department only three weeks ago that he was being held in Iran.

London-based news website IranWire, which first reported White’s arrest, quoted a former detainee, Ivar Farhadi, as saying he had been held at the same prison, Vakilabad, in Mashhad, northeastern Iran.

Farhadi told IranWire White’s life was in danger because he was being kept in a prison with dangerous criminals.

Joanne White told the New York Times her son, a California resident, suffers acute asthma and had had chemotherapy and radiation treatment for a neck tumor.