Iran's top nuclear official Ali Larijani has sent the countries' foreign ministers a letter "insisting on the necessity of negotiations", the official IRNA and the semi-official Mehr agencies reported.

Negotiations between Iran and the so-called EU-3 broke off in August when Iran resumed its uranium conversion programme in defiance of international calls to keep such activities frozen.

Larijani said in the letter that Iran would "welcome negotiations that are constructive and based on logic".

The letter is the first approach that Larijani has made to the EU-3 since taking over the nuclear dossier from the pragmatic cleric Hassan Rowhani after Mahmoud Ahmadinejad became president in June.

Talks broke down last summer after the EU-3 demanded a total halt to fuel cycle work in exchange for a package of trade, security and technology incentives.

Iran maintains such work for peaceful purposes is a right of any signatory of the nuclear Non-Proliferation Treaty.

Iran rejected the deal and in protest resumed uranium conversion activities, the first step in making enriched uranium, which can be used to fuel power reactors but can also be the raw material for nuclear bombs.