Iran's defiant expansion of its nuclear programme and 10 failed meetings with the IAEA will dominate a gathering of the UN body's board starting Monday, diplomats and analysts said.
The 35 nations that make up the Vienna-based International Atomic Energy Agency's rotating board of governors were expected to refrain however from passing a resolution condemning the Islamic republic.
The IAEA's latest quarterly report, circulated on May 22, showed that despite numerous IAEA board and UN Security Council resolutions calling for a suspension, Tehran has continued to expand its nuclear activities.
In particular, and in spite of sanctions aimed at preventing such advances, it has boosted its capacity to enrich uranium, which in its highly purified form can be used in a nuclear weapon. Iran says it needs the material for power generation and medical isotopes.
Iran has also converted a portion of its medium-enriched uranium into another form in order to make reactor fuel, the IAEA report showed, which is difficult -- but not impossible -- to convert back.
But analysts say the rate of conversion is too low to prevent Iran's uranium stockpile from growing, that its output could triple once new machinery is up an running and that Tehran is producing more than it currently needs.
This conversion of 20% enriched uranium "is a ray of light but there are still some pretty dark clouds around," Shannon Kile, nuclear expert at the Stockholm International Peace Research Institute (SIPRI), told AFP.
One such source of additional worry is Iran's progress, also outlined in the latest IAEA report, in building a new reactor at Arak which could in theory provide Iran with plutonium, if the fuel is further processed.
Plutonium is an alternative to highly enriched uranium for a nuclear weapon. North Korea used plutonium in two tests in 2006 and 2009, while a uranium bomb was dropped by the US on Hiroshima, Japan in 1945.
Arak "shows that this issue is not just about 20-percent enriched uranium stockpiles. This is a broader picture," said one senior Western diplomat in Vienna.
Another bone of contention meanwhile is what the IAEA suspects may have been Iranian research, mostly before 2003 but possibly ongoing, into creating a nuclear payload for a missile, including at the Parchin military base near the capital.
Iran denies this, and 10 meetings, the latest on May 15, with the IAEA since its major November 2011 report summarising these claims -- based mostly, but not only, on foreign intelligence -- have failed to make progress.
Wendy Shermann, the US representative in six-power talks with Iran, currently on hold until after elections on June 14, told the Senate Foreign Relations committee this month that "at some point", the IAEA would have refer the issue to the UN Security Council.
But the IAEA's board, at this meeting at least, is expected to refrain from upping the ante, in part because of the Iranian elections, with the P5+1 powers -- the US, China, Russia, Britain, France and Germany -- preferring to keep their powder dry for now.
"If I interpret the tea leaves correctly from the P5+1, the powers will essentially be prepared to kick the can down the road, at least for another few months," Mark Hibbs, analyst at the Carnegie Endowment for International Peace, told AFP.