Delegations from 35 countries will attend a Tehran conference on nuclear disarmament, Iranian Foreign Minister Manouchehr Mottaki was quoted as saying on the IRINN Web site.
Mottaki said the conference will be attended by 300 guests, nuclear scientists and journalists.
The conference will be held April 17-18. Previously, Iranian officials said 60 will take part.
According to Mottaki, the conference will hold an exhibition devoted to the Hiroshima tragedy.