The world's big powers have been told to expect a formal response as soon as today from the Tehran government that sets out an initiative designed to restart negotiations over Iran's nuclear programme.

The letterfollows a conversation yesterday between Javier Solana, the European Union's foreign policy head, and Saeed Jalili, Iran's chief nuclear negotiator, that was described by Mr Solana's office as inconclusive. Further talks "were not ruled out", a spokesman said.

Iranian state television said Mr Jalili "stressed the continuation of talks" and "contacts" in the phone call.