The whereabouts of Robert Levinson have been a mystery since Washington said he went missing in March while on a business trip to the southern Iranian island of Kish.
State Department spokesman Tom Casey said the Iranians had conducted an investigation but not shared any findings with Washington or with the Levinson family.
“We think his family and we are owed a full accounting of what information the Iranian government has,” he told reporters.
“We certainly hope that they will be willing to do so when Mrs Levinson and members of the family travel there,” Casey said.
Levinson’s wife Christine, their son Daniel, and other relatives plan to visit Tehran shortly to press the Iranian government on the case.
They have applied for their visas and hope to fly out next week, the State Department spokesman said.
The US government normally frowns on travel to the Islamic republic by its citizens, but Casey said this a “fairly unique case” and the trip “might provide some encouragement” to the Iranian authorities to divulge information.
“We certainly would hope that despite the many issues in our relations with Iran, that the Iranian government would want to help find him and help his family… and hopefully see them reunited,” he added.
Levinson, who retired from federal service 10 years ago, went missing on March 8 on Kish, the same day that he arrived on the island on an Iranian airline and checked into a hotel, according to his wife’s website.
Kish off Iran’s southern coast is a free-trade zone and is being heavily promoted by the authorities as a resort with attractive beaches and diving.
In contrast to mainland Iran, most foreign nationals do not require a visa for short stays on Kish.
Iran has always said it had no record of Levinson even entering the country, and that any information it does have has been relayed to the US government through the Swiss embassy in Tehran, which represents US interests in Iran.
In September, the Washington Post reported that Iran blocked a request by Swiss diplomats to visit Kish to look for traces of the missing American, in particular his luggage.
