The six world powers trying to get Iran to give up strategic nuclear fuel work meet in Berlin on Thursday to figure out how to handle a defiant Tehran, with the United States pushing for UN sanctions.
It is the first meeting of permanent UN Security Council members Britain, China, France, Russia and the United States, plus Germany, since Iran failed on August 31 to honour a Council deadline to halt uranium enrichment, the process which makes nuclear reactor fuel but also atom bomb material.
The six are offering Iran talks on a package of trade, security and technology benefits if it freezes enrichment.
In Berlin, "they're going to talk about sanctions, and my guess is that they're going to come up with not very much," Chicago-based non-proliferation expert Gary Samore said about the meeting of the six nations' foreign ministry political directors.
A Western diplomat agreed, saying the gathering was "not a decision-making meeting. It is the first conversation on where we go from here."
Washington leads international concerns that Iran is covertly trying to develop nuclear weapons, something Tehran denies, as well as the push for sanctions.
But Iranian allies and major trading partners Russia and China are reluctant to take such measures, fearing they will worsen the current confrontation or even lead to war.
The Berlin meeting comes after an EU-Iran effort to kickstart negotiations over Tehran's nuclear programme and give it a chance to avoid UN sanctions were postponed at the last minute in Vienna on Wednesday.