By Jonathan Marcus
BBC diplomatic correspondent
Two reports on Iran's nuclear activities - one last week from the International Atomic Energy Agency (IAEA) in Vienna and the second on Tuesday from respected London-based think-tank the International Institute for Strategic Studies, raise questions over Iran's nuclear programme and where diplomatic efforts to contain it go from here.
Iran has all along insisted its nuclear programme is peaceful
This is a slow-burning diplomatic crisis.
Certainly there will be punctuation marks of tension along the way - one could be coming up in a little under two weeks' time - when the IAEA board meets again with every chance that the US and EU participants will push for Iran to be reported to the UN Security Council.
But the good news for diplomats in the think-tank report is that Iran is assessed to be several years away from being able to produce sufficient nuclear material for a bomb.
Iran insists it only wants a civil nuclear programme. So what exactly has it done wrong?
Record of concealment
The IAEA report makes it clear that Iran failed to disclose, as it was obliged to do under the NPT treaty, a good deal of information about its nuclear activities for a period of nearly 20 years.
NUCLEAR FUEL CYCLE
Mined uranium ore is purified and reconstituted into solid form known as yellowcake
Yellowcake is converted into a gas by heating it to about 64C (147F)
Gas is fed through centrifuges, where its isotopes separate and process is repeated until uranium is enriched
Low-level enriched uranium is used for nuclear fuel
Highly enriched uranium can be used in nuclear weapons
The agency still has outstanding concerns about the source of contamination at certain sites in Iran and about the extent of the country's efforts to import and manufacture the centrifuges essential for the enrichment process.
It has bluntly stated that "Iran's full transparency is indispensable and overdue".
It is this past record of concealment that adds considerably to concerns about Iran's long-term nuclear ambitions.
And that's why the Europeans - belatedly backed by the Americans - want to persuade Iran to abandon its enrichment programme altogether.
Iran's recent decision to resume conversion activity, a step short of enrichment, broke its understanding with the EU and may well precipitate a referral to the UN Security Council.
But even Iran's strongest critics are likely to press for a modest series of steps from the UN in an effort to maintain as broad a coalition as possible.
The hope is that such a coalition will persuade Iran that it has much to lose if it pursues its enrichment programme.
But equally the Iranians may feel emboldened by America's problems in Iraq and the high oil price to ratchet up the pressure.
The diplomatic brinkmanship looks set to continue for some time to come.