New York (CNN) -- The family of retired FBI agent Robert Levinson can't help but count the days since he vanished during a business trip to Iran's Kish Island on March 8, 2007.
Saturday marked 2,024 days since he's been gone.
"Every day I miss him," said Christine Levinson, his wife of 38 years. "I wake up and his side of the bed is empty."
She left her Florida home this week to travel to New York in hopes of making a personal plea to Iranian President Mahmoud Ahmadinejad, who is attending this week's U.N. General Assembly. Levinson 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 Levinson family says Robert 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.
Last year, the Iranian government said it would make inquiries about Levinson but did not know what happened to him.
Digital billboards were posted in Times Square this week with Levinson's picture and a message to U.N. delegates asking for help in finding him.
"Because the U.N. General Assembly is here, we can get the world to help us," Christine Levinson said.
The FBI has offered a $1 million reward for information leading to his safe return. His wife has also met with President Obama.
"He said that he would help any way that he could," and that "he would put the full force of the U.S. government behind helping to get Bob home," she said.
It's believed Levinson, now 64, is being held captive. U.S. officials believe he is somewhere in southwest Asia. It's unclear who is holding him.
"There is every reason to believe based on all the evidence that Levinson is alive and well," a source with knowledge of the case said. The source would not provide further details.
In a so-called "proof of life" video released last year but apparently made two years ago, Levinson appears about 50 to 60 pounds lighter. He stares and blinks as he looks into a camera and says he "is not in very good health."
He refers to 33 years of service to the U.S. government and asks the United States to "answer the requests of the group" that has been holding him. Who the group is and what they want is unknown.
"Please help me get home," Levinson says on the tape.
Christine has sent several emails to the address where the proof-of-life video came from to ask the senders what they want.
"They have not responded. We have not heard back from them since then and that was almost two years ago. So it's very difficult," she said.
Levinson said she sees her husband's determination every time she looks at that video.
"It gives me hope that I'll see him again soon. And comfort that I can at least say to the picture, 'I love you.'"
The Levinsons have seven children and two grandchildren. One daughter was married last year. Her brother stood in for their father and walked her down the aisle. Levinson has also missed a son and daughter's high school and college graduations.
"They both wore yellow ribbons and carried pictures of Bob to the graduations just to keep him in our prayers," Christine Levinson said.
She said she hopes to deliver this message to Iran's leader: "Please help my family to become whole again. We need Bob home as soon as possible."
CNN's Jill Dougherty contributed to this report.