Iran and world powers kicked off a new round of nuclear talks today hoping to make enough progress to move up a gear and start drafting a historic final deal next month.
Threatening to drive a wedge between the powers, however, is the crisis surrounding Ukraine, which has led to the biggest standoff between Russia and the West since the end of the Cold War.
Iran and the five UN Security Council permanent members plus Germany want to transform a deal struck in November into a permanent agreement by the time this temporary accord lapses on July 20.
Doing so is a tall order, however, requiring both sides to tackle thorny issues that will severely test their willingness and ability to give ground to the limit.
So far the mood music has been good, with the powers' chief negotiator, EU foreign policy chief Catherine Ashton, hailing the last monthly round in mid-March as "substantive and useful".
Likewise Iranian Foreign Minister Mohammad Javad Zarif told Iranian media afterwards that "there are signs that an understanding is possible that respects the rights of the Iranian nation."
A senior US official involved in the talks said on Friday she was "absolutely convinced" a deal could be reached and that both sides were "looking toward beginning drafting (a deal) in May".
But "the real issue is not about whether you can write the words on paper, do the drafting. It's about the choices that Iran has to make, and some of them are very difficult."
Under the November deal, which took effect on January 20, Iran froze certain nuclear activities for six months in exchange for minor relief from sanctions hurting its economy.
As part of the deal, Iran was given greater access to civilian aircraft parts and yesterday Washington said that Boeing had been issued with a temporary licence to do business with the Islamic republic.
Now the powers want Iran to reduce permanently, or at least long-term, the scope of its programme in order to make any dash to make the bomb extremely difficult and easily detectable.
