The US government has denied media reports that Bob Levinson was working for the CIA when he disappeared in Iran about seven years ago.
Levinson vanished after a March 2007 meeting with an admitted killer on Kish Island, an Iranian resort.
For years, the US publicly described him as a private citizen who traveled to the tiny Persian Gulf Island on business.
But an Associated Press investigation revealed that Levinson was actually a contractor working for the CIA.
AP says he was paid by a team of agency analysts who were acting without authority to run spy operations to gather intelligence.
But White House spokesman Jay Carney rejects the allegation.
"I'm not going to comment on every allegation in that story. I would say that, if there's somebody detained overseas and it is published, true or false, that he's working for the CIA, I think it is dictated by logic that that very likely puts that person in greater danger. What I can tell you is he was not a US government employee when he made that trip."
If Levinson is still alive at age 65, then he has been held captive longer than any other American known to be held overseas.
Both US lawmakers and the Levinson family have urged the Obama administration to find the missing man and release more details about the case.
Carney declined to discuss the case in detail but said numerous US officials, including President Barack Obama, have pressed Iran for help on finding and returning Levinson.
Iranian President Hassan Rouhani has said publicly he has no information about Levinson's whereabouts.