Just why Robert Levinson, a former Federal Bureau of Investigation agent and now private investigator, should venture into Iran to meet a American fugitive wanted for murder in the US remains a mystery that the highest Bush administration authorities are trying to unravel.

As the Financial Times revealed this week, Mr Levinson disappeared on March 8 after a six-hour meeting on the Iranian island of Kish with Dawud Salahuddin, an American who converted to Islam and was recruited by revolutionaries to assassinate an Iranian opposition activist near Washington in 1980.