FBI spokesman Rich Kolko said Monday the agent had retired nearly a decade ago and appeared to be in Iran on private business. He said the missing man was last seen there in early March and was not working for the FBI as a contractor.

"At this time, there are no indications that this matter should be viewed other than as a missing person case," Kolko said.

Kolko also said the former agent had worked on traditional criminal issues such as organized crime cases—drawing a distinction between those and international terrorism or intelligence work that could have taken him to Iran.

State Department spokesman Sean McCormack said the United States saw no connection between the missing man and the current crisis between Iran and Britain over 15 British sailors and marines seized last month by Iranian forces.

The department has sent a letter to the Iranians through diplomatic intermediaries, asking if authorities there have any information about the man, McCormack said.

He said the State Department had been in constant contact with the man's family and his employers since he was reported missing, but the spokesman did not say why it had taken three weeks to get in touch with Iran about the case.

"It's an American private citizen who is in Iran on private business about whom we are pursuing welfare and whereabouts (information)," McCormack told reporters. "We have been monitoring this situation for a couple of weeks now."

The Bush administration has increased diplomatic and other pressure on Iran in recent months, including added naval power in the Persian Gulf, while also making new overtures. Secretary of State Condoleezza Rice is expected to sit down soon for international talks with Iran's foreign minister over the violence in neighboring Iraq.

Washington and Tehran do not have diplomatic relations and U.S. interests in the country are represented by Switzerland.

Citing privacy concerns, McCormack declined to give details about the name, age or occupation of the missing man.

The man was last heard from around March 11 while in a coastal area of southern Iran on or near Kish Island, where he was apparently working on a project for an independent filmmaker.

U.S. citizens are not barred from traveling to Iran but must obtain a visa, although Kish Island is a Persian Gulf resort area and free- trade zone for which no Iranian visa is required.

A State Department official said the man is not of Iranian descent and that "welfare and whereabouts" requests for U.S. citizens reported missing in Iran average about two to three per year.

Associated Press writer Lara Jakes Jordan contributed to this report.