New York (CNN) -- Iranian President Mahmoud Ahmadinejad insists his government does not know the whereabouts of the American retired FBI agent who disappeared in Iran five and a half years ago, but that Iranian officials continue to assist in the effort to find him and send him home.
Robert Levinson vanished during a business trip to Iran's Kish Island on March 8, 2007. His family says he was working as a private investigator looking into cigarette smuggling in Iran when he went missing. The State Department has repeatedly denied he was working for the government and has urged Tehran to find him.
Christine Levinson, Robert's wife of 38 years, travelled from her home in Florida, New York, this week in hopes of making a personal plea to Ahmadinejad, who is attending this week's U.N. General Assembly.
Ahmadinejad did not meet with her, but did answer questions posed by CNN on Thursday, 2,030 days since Levinson's disappearance.
"They told me (Levinson) was in Iran, and of course the question came up in my mind, what was an American intelligence officer doing in Iran," Ahmadinejad said, but added that the Iranian government had granted Levinson's family permission to come meet with investigators.
"They held meetings, and I directed them. (I) directed the intelligence agencies in Iran to cooperate with their American counterparts. They've had meetings. They've held dialogues, but I'm not aware of the results," he said.
Ahmadinejad told CNN he could not confirm Levinson was alive or even in Iran.
"An individual is lost, how are we supposed to find him among 7 billion people spread across the globe? What we can do is assist, help and cooperate, which we have been doing, and we are doing... as a humanitarian gesture and action."
Christine Levinson, who has met with President Obama, is convinced Ahmadinejad can help in the search for her husband.
"In the past he has said that he will investigate and he will have his people investigate," Levinson told CNN. "He has promised to help us. So we need to get him in touch with whoever can help us get the job done and get Bob home."
The FBI has offered a $1 million reward for information leading to Levinson's safe return.
"We don't want anyone to be far away from their family," Ahmadinejad said, "but we must all help. Let's not make this another tool by which to lay accusations at the feet of other countries."
U.S. officials believe Levinson, now 64, is being held captive somewhere in southwest Asia. While it's unclear who is holding him, a source with knowledge of the case said based on the evidence there is every reason to believe that Levinson is alive and well.
CNN's Susan Candiotti, Ross Levitt, and Fernando Del Rincon contributed to this report