Iran Nuclear Deal Reached in Vienna, Say Diplomats

A comprehensive deal on Iran's nuclear programme has been reached, diplomats in Vienna say, bringing to an end a 12 year stand-off that had threatened to trigger a new war in the Middle East, and potentially marking the beginning of a new era in relations between Iran and the west.

An announcement on the agreement is due later on Tuesday morning, on the 18th day of almost uninterrupted negotiations in Vienna, involving foreign ministers from seven countries and the EU's foreign policy chief, Federica Mogherini.

The ministers - from Iran, the US, UK, Russia, China, France and Germany - are expected to gather for a final photo mid-morning. At that time, they may issue a short statement, diplomats said, followed by a press conference at noon local time (11am BST).

There are still discussions underway among the parties on whether the formal announcement should be at the photo, or at the press conference.

At some point it is expected President Obama and his Iranian counterpart, Hassan Rouhani, will make statements from their capitals.

It is not clear how much of the estimated 100 pages of text, including five annexes, will be published on Tuesday. Much of the outline of the agreement is already known, having been provisionally settled in Lausanne in April.

It involves Iran accepting curbs on its nuclear programme in return for sanctions relief, but many of the critical, politically-charged details will only be made public on Tuesday.

In particular, it will become clear whether the arms embargo and missile programme restrictions on Iran will remain in place and at what point the agreement will be codified as a UN security council resolution.

The full agreement, known as the joint comprehensive plan of action, is likely to come under instant and ferocious attack from its opponents - mostly in the US, Iran and Israel - but its defenders portray it as one of the most important arms control accords of modern times and a rare diplomatic success in the Middle East.

On Monday, the Iranian president's office was forced to delete a premature tweet in his name that appeared to welcome a nuclear agreement which had yet to materialise.

The deleted tweet on the English-language account under president Hassan Rouhani's name declared: "#IranDeal is the victory of diplomacy & mutual respect over the outdated paradigm of exclusion & coercion. And this is a good beginning."

Soon after, a new tweet was posted in its place, adding the word 'if' at the beginning.

As the Monday evening target came and went, Iran's foreign minister, Mohammad Javad Zarif, appeared on the balcony of the hotel venue and faced shouted questions from the journalists in the street below.

Asked how he was feeling, Zarif replied: "Sleepy and overworked." Asked if there would be a deal on Tuesday, he said: "It is possible."

Once an agreement is announced, it will not take effect for some time: it must first survive a trial by fire from its critics in Washington and Tehran.

The greatest hurdle will be the US Congress, where Republicans have a majority and are expected to vote against the deal after a review period of up to 60 days. They will seek to win over 12 Democrats in an attempt to defeat a presidential veto.