Iran has told the United States that it has no information of the missing American identified as Robert Levinson who went missing in Iran in March, State Department deputy spokesman Tom Casey said at a briefing on Friday.

"They once again claim to have no information about him and that is unfortunate and we believe that there are many possible leads out there for them to purse including a number of things reported in the past," Casey said at a briefing.

"We are going to continue to be pursuing this, but unfortunately the Iranian government's response to date on this has again been to simply say they have no information, and which I don't think is very credible," Casey said.

Washington has no diplomatic relations with Teheran since April 1980, five months after Iranian students occupied the American embassy in Teheran. Fifty-two Americans were held hostage for 444 days.

Levinson, 59, retired from the FBI in 1998.

Source: Xinhua