Under the terms of the agreement, Iran is to sign an additional protocol allowing intrusive short-notice inspections of its facilities, give detailed answers to all UN questions about its nuclear programme and indefinitely suspend uranium enrichment activities. It says the concessions are being made as a gesture of goodwill and are wholly unaffected by the 31 October deadline set by the International Atomic Energy Agency (IAEA), which Iran refused to accept.

In return, the European leaders made no concrete promises, but they did confirm Iran’s right to develop a civilian nuclear programme and said that once international concerns about the programme were allayed, Iran would find it easier to gain access to nuclear technology.

The agreement is the result of months of back-stage diplomacy by the European ministers, who made the offer of technology in exchange for transparency in August. Since then, they have publicly joined the US in demanding Iran sign the protocol and fully declare the extent of its nuclear activities.

Washington has cautiously welcomed the development, which UK Foreign Office officials said was achieved with the help of the US State Department. ‘It looks like they’re accepting the demands of the free world and now it’s up to them to prove that they’ve accepted the demands,’ said President Bush.

The deal effectively nullifies the IAEA’s 31 October deadline, but pitfalls remain. Iran must act on its promises – and gain IAEA verification that it has done so. There is deep suspicion in Tehran of the IAEA, which is seen as potential cover for US or Israeli espionage.

There are two areas likely to cause further problems and disagreement: the level of access nuclear inspectors get to military facilities – something the US is likely to press hard for and Iran to strongly resist; and the extent of Iran’s suspension of uranium enrichment activities. The statement agreed on after the ministers’ meeting with Rohani said the activities to be suspended would be those defined by the IAEA, but Iran insists on its right to enrichment and says the suspension will end when it feels the time is right.

Although Rohani is part of the conservative establishment and had the direct authority of Supreme Leader Ali Khamanei, sections of the hardline conservative press reacted with anger to the deal.