An EU spokeswoman has said that a scheduled meeting with Iran over the country's nuclear program will go ahead despite the resignation of Tehran's chief negotiator, Ali Larijani.
A deputy foreign minister, Saeed Jalili, has been drafted in to replace Mr Larijani in time for Tuesday's talks with EU foreign policy chief Javier Solana.
Cristina Gallach said that a change of negotiator could complicate attempts to resolve Iran's nuclear issue.
However, she added that it was too soon to judge Mr Larijani's replacement.
Iranian President Mahmoud Ahmadinejad finally accepted Mr Larijani's resignation yesterday.
A government spokesman said there would be no change in Iran's atomic programme.
Despite several meetings during the past year, Mr Larijani and Mr Solana have not overcome the deadlock over Tehran's refusal to suspend its sensitive uranium enrichment activities.
Mr Solana must report to major world powers Britain, France, Germany, Russia, China and the US before mid-November on Iran's willingness to give up uranium enrichment in exchange for political and trade incentives.
The West believes Iran's nuclear programme is cover for a drive to develop an atomic bomb, but Tehran insists it is for civilian objectives only.
