Khatami canceled plans to attend a nuclear disarmament conference in Japan, with his aides giving the travel ban as the reason, the BBC reported.
Known as a moderate when he served as president from 1997 to 2005, Khatami backed the opposition to his successor, Mahmoud Ahmadinejad, during last year's election. After Ahmadinejad won with a reported lopsided majority, he charged the count was fraudulent.
The BBC reports that the government has been trying to restrict Khatami and other high-profile opponents, imposing travel bans and using the Basji militia to intimidate them from appearing at rallies. But the government has avoided arrests of major leaders, although hundreds of their followers have been detained.