Senator John McCain has suggested the CIA has not been forthcoming with the Congress on details about an American who disappeared while on a secret intelligence mission to Iran.
Iran's foreign minister asserted that Robert Levinson is "not incarcerated by the government and I believe the government runs, pretty much, good control of the country".
An Associated Press investigation published this past week found that Levinson was working for the CIA - investigating the Iranian government. The US long has publicly described Levinson as a private citizen who travelled to an Iranian island on private business.
McCain, R-Arizona, told CNN's State of the Union that "the CIA did not tell the truth to the Congress" about Levinson.
McCain said he is confident the US is doing all it can to learn what has happened to Levinson. But he said he is disturbed the Obama administration has not been more forthcoming with information about him.
He said he doesn't "think there's any doubt" about whether Iran knows Levinson's fate.
But Foreign Minister Javad Zarif, asked on CBS' Face the Nation where Levinson is, replied: "I have no idea."
"If we can trace him and find him, we will certainly discuss" returning him to the United States, he added, though he made clear that "we have no traces of him in Iran".
Secretary of State John Kerry dismissed a suggestion by Levinson's family that the US government was not doing enough to find out what happened to Levinson.
"There hasn't been progress in the sense that we don't have him back. But to suggest that we have abandoned him or anybody has abandoned him is simply incorrect ... and not helpful," he told ABC's This Week.
"The fact is I have personally raised the issue not only at the highest level ... but also through other intermediaries. So we don't have any meeting with anybody who has something to do with Iran or an approach to Iran where we don't talk to them about how we might be able to find not just Levinson, but we have two other Americans that we're deeply concerned about."
Right now, "we're looking for proof of life", Kerry said.
Iran's press counsellor at the United Nations called on Washington to explain Levinson's mission in Iranian territory, after the AP investigation revealed that he had been on an unauthorised assignment for the CIA when he vanished on Iran's Kish Island in March 2007.
US officials have raised the Levinson case with Iran repeatedly over the years. But until the AP investigation was published, it was not known that Levinson was hoping to gather information in his role as an independent contract investigator who expected to be compensated by a group of analysts at the CIA.
After he vanished, the CIA at first told lawmakers he had previously done contract work for the agency, but he had no current relationship with the agency and there was no connection to Iran. However, in October 2007, Levinson's lawyer discovered emails in which Levinson told a CIA friend that he was working to develop a source with access to the Iranian government. The emails were turned over to the Senate Intelligence Committee, which touched off an internal CIA investigation.
Three veteran analysts were forced out of the CIA and seven others were disciplined as a result of a breach of agency rules.
The last photos and video of a bearded, emaciated Levinson were released anonymously to his family in 2010 and early 2011. Investigators say his trail has grown cold since.