Ali Larijani, who quit as Iran's chief nuclear negotiator, and his replacement will go to talks with the European Union's Javier Solana to try to defuse a row with the West, the Foreign Ministry said this morning.
Mr Larijani's resignation was announced yesterday, a move analysts said exposed a rift with President Mahmoud Ahmadinejad about how to fend off pressure from the West which accuses the Islamic Republic of seeking atomic bombs. Tehran denies this.
Analysts said the change would strengthen the president's hand in pushing a harder line. One diplomat was wary about the appointment of Saeed Jalili, a presidential ally, as the new negotiator, saying he "specialises in monologue" not debate.
Mr Larijani had been scheduled to go to Rome on Tuesday to meet Solana, the EU foreign policy chief representing six world powers in attempts to resolve the nuclear standoff.
Foreign Ministry spokesman Mohammad Ali Hosseini said Larijani and Jalili, a deputy foreign minister, would attend but said it was not clear if both would go to future meetings.
Iranian analysts said Mr Larijani's presence could be part of a handover plan or to show he was not quitting under a cloud.
Mr Hosseini said the reshuffle did not signal any new policy.
"The other parties must not misinterpret the resignation. We have stressed this time and again, all Iranian officials have said the same, that the nuclear matter is a national dossier," Mr Hosseini told a news conference.
He said the pursuit of peaceful nuclear technology was part of Iran's "unchangeable goals".
The final say in nuclear and other policy lies with Supreme Leader Ayatollah Ali Khamenei. But analysts said changing such a top post would need his approval and Jalili's appointment indicated support for the president and his position.
The reshuffle comes at a sensitive time when the West is seeking to impose further sanctions on Iran for refusing to halt uranium enrichment, a process that can make fuel for power plants or, if Iran wanted, material for warheads.
Major powers have agreed to delay such a move until November to see if Iran cooperates with the UN nuclear watchdog, the International Atomic Energy Agency, to answer queries about Tehran's intentions and to await a report from Solana.