MIAMI, Florida (CNN) -- It has been a year since retired FBI agent Robert Levinson disappeared in Iran, and his family still has no idea where he is.

Bob Levinson's daughter Susan and his wife Christine Levinson speak at a rally for the ex-FBI agent Sunday.

Christine Levinson, his wife of 33 years, and their family and friends staged a "rally of hope" in their South Florida hometown of Coral Springs on Sunday -- a day before his 60th birthday.

Outside a restaurant whose owners know and miss Bob Levinson, a crowd gathered wearing yellow ribbons. They signed a petition that will be sent to Iran's Grand Ayatollah Ali Khamenei, appealing for the Iranian leader to help find their missing relative.

"The rally of hope is to let everyone know that we have not forgotten Bob, that we will continue to search for him and that we hope that anyone that might have information about him will get in touch with us ... and help us bring him home," Christine Levinson said. Watch an interview with Christine Levinson »

She urged anyone with information to contact the family at www.helpboblevinson.com.

Levinson worked 30 years for the FBI and U.S. Drug Enforcement Administration and was employed as a private investigator at the time of his March 8, 2007, disappearance, the site says.

Levinson's family has said they think he might have been working on a cigarette-smuggling case when he flew to Kish in Iran from Dubai.

But Sunday, his wife said she's not totally sure what he was doing in Iran.

"He may have met with someone there and the two may have been abducted and questioned," the Web site states. "Some reports suggest the other man was released but Levinson was not."

Levinson was last seen on Kish Island, off the coast of southern Iran.

Dawud Salahuddin, an American fugitive who lives in Iran, said last year that he met Levinson in a hotel on Kish Island on March 8, 2007.

Salahuddin says the meeting was an effort to put Levinson in touch with Iranian authorities to help the American investigate cigarette smuggling as part of his contract work for a tobacco company.

Known in Iran as Hassan Abdulrahman, Salahuddin is not believed to be a credible source of information about Levinson, senior U.S. administration officials have said.

Salahuddin was given refuge in Iran after admitting to killing a former pro-Western Iranian diplomat in Maryland in July 1980. He was on assignment from Ayatollah Ruhollah Khomeini's new regime when he killed Ali Akbar Tabatabai at his residence in Bethesda, according to Time magazine.

Shortly after admitting the killing in a 1995 interview with a reporter for the National Security News Agency, Salahuddin began working as a journalist for the Iranian government's news agency in Tehran in 1980. According to Time, Salahuddin was in Afghanistan during much of the mid- to late-'80s, fighting Soviet forces with mujahedeen fighters.

Salahuddin has repeatedly expressed a desire to return to the United States.

Salahuddin's account of his meeting with Levinson is that he was seized by plainclothes Iranian officials, who took him away from the room he shared with Levinson to question him about his Iranian passport.

When he was freed the following day, Salahuddin said, he was told by officials that Levinson had returned to Dubai.

Christine Levinson said a man purporting to be Salahuddin called her "right when he disappeared" and told her that he would be home in a few days.

Senior administration officials have said they suspect Iranian authorities seized Levinson, although they have no proof.

State Department concerned

The State Department has sent several letters to the Iranian government seeking information about Levinson. The Iranian government continues to maintain it has no information about him.

Speaking last week at a daily briefing, State Department spokesman Tom Casey said the United States is "baffled by the lack of support" from Iran on trying to locate Levinson.

"This isn't a political issue; this is an issue about an individual ... who went missing from Iran, a place where there are very close tabs kept on foreigners, and in a situation in which we certainly have concerns that a year has gone by and we have not heard from him," he said.

The United States has no diplomatic ties with Iran but sends messages through the Swiss Embassy. The United States will "continue to push them, but unfortunately, they hold the key here," Casey said.

In December, Christine Levinson traveled to Iran to seek information about her husband's disappearance and pressure the government on his case. While the Iranian government was polite and guaranteed the security of her family during their trip, she said, they provided no details on his whereabouts.

A hotel registration indicates Levinson checked in and out of a hotel on Kish Island on March 8-9 last year. Christine Levinson says she saw his signature. She was told he left in a cab.

She is especially worried about her husband's fate. He has high blood pressure and diabetes for which he takes medication, she said, adding that his medication was found in a hotel room in Dubai where he was staying before making what was to be a day trip to Kish Island.

In February, she hired an Iranian lawyer to "make sure the Iranian government does not forget about Bob."

"I know that [the attorney] can file the papers necessary to report that he's missing," she said, referring to her attorney. "And he can ask them to do things and go with them to look in prisons and jails.

"Whatever might be necessary."

"Happy Birthday" sung

Among those at Sunday's event: the head of the local FBI office, the county sheriff, and former federal agents and prosecutors who worked with Levinson at the DEA and FBI.

Daniel Levinson, who accompanied his mother to Iran last year, spoke with pride about his Dad, reading letters from Sen. Bill Nelson and Florida Rep. Robert Wexler. In Farsi, the younger Levinson said, "The next time I go to Iran, I hope it will be to bring my father home."

Daniel's aunt Susan said he learned Farsi after his father disappeared.

Monday is Robert Levinson's 60th birthday. The family sang "Happy Birthday" in the parking lot.

Christine Levinson said that when she needs a lift, she phones her husband's voice mail and hears, "Hello, this is Bob Levinson. ... Please leave your name and the time of your call, and I'll get back to you. Take care, and have a nice day."

"In the moment when I listen, it makes me sad," she said. "But then it makes me keep going because I know I will hear him again in person."

"Each day, I get up and hope today will be the day that I'll bring him home," she said. "And if that doesn't happen and if I haven't gotten a phone call, I focus on what I'm going to do next to find him." E-mail to a friend

CNN's Elise Labott contributed to this report.

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