By Paul Reynolds
World affairs correspondent, BBC News website
President Mahmoud Ahmadinejad says Iran's intentions are peaceful
The Iranian nuclear confrontation will just not go away.
The latest report from the International Atomic Energy Agency (IAEA) that Iran is not cooperating fully in the investigation of its nuclear activities leaves this potentially serious crisis open.
Iran is featuring heavily in the US presidential campaign, with the presumptive Republican nominee John McCain frequently suggesting that Democratic hopeful Barack Obama, who has proposed talks with Iran, is showing weakness.
The issue is likely to remain an important one for whoever is the next president - assuming the Bush administration does not take military action in its final months.
The problem at the moment is not just Iran's refusal to suspend the enrichment of uranium, in defiance of UN Security Council demands and three rounds of UN sanctions.
The immediate concern of the new IAEA report is Iran's apparent reluctance to give its full cooperation in the investigation to sort out exactly what it has been up to in the past.
This effort is needed in order to satisfy the demands of the IAEA and the Security Council that Iran has given up all suspicious activities.
Iran says it has answered all questions and that its intentions are entirely peaceful.
In particular, the IAEA has been concerned about the acquisition by Iran, probably from the Pakistani nuclear scientist AQ Khan, of a 15-page document describing, as the IAEA puts it, "the procedures for the reduction of UF6 [uranium hexafluoride] to uranium metal and the machining of enriched uranium metal into hemispheres, which are components of nuclear weapons".
Iran has told the IAEA that this design document was received along with the P-1 centrifuge [machines that enrich uranium] documentation in 1987 and that it had not
been requested by Iran.
The IAEA has a copy of the document but has not apparently been able to discuss its contents fully with the relevant people in Iran. It says the weapons design question needs "substantive explanations".
Until this is cleared up, the suspicion will be that Iran has been interested in nuclear weaponisation. And if it was once, it might be again.
In the meantime, a new attempt to get Iran to suspend enrichment will be made by the EU's chief foreign policy representative, Javier Solana. He hopes to go to Tehran soon with an improved offer of incentives if Iran does agree to suspension.
For its part, Iran is reported to be offering a joint venture on enrichment with foreign partners, but on Iranian soil.
The effect of all this uncertainly is being felt not just in the US presidential campaign.
The International Institute for Strategic Studies (IISS) has published a report that draws attention to the sudden interest in nuclear energy by 13 countries across the Middle East.
"This upsurge of interest is remarkable, given both the abundance of traditional energy sources in the region and the low standing to date of nuclear energy there," said IISS Director General Dr John Chipman.
Until this is cleared up, the suspicion will be that Iran has been interested in nuclear weaponisation
"Notwithstanding the legitimate energy and economic motivations behind this sudden region-wide interest in nuclear power, political factors also play an important role...
"The single most salient political factor... is Iran's development of dual-use nuclear technologies, which motivates at least some of its neighbours to seek fledgling nuclear capabilities of their own.
"If Tehran's nuclear programme is unchecked, there is reason for concern that it could in time prompt a regional cascade of proliferation among Iran's neighbours.
"A proliferation cascade would become more likely if Israel felt obliged to relinquish its long-standing doctrine of nuclear 'opacity' or ambiguity... as this would increase the pressure on Egypt and perhaps other Arab states to seek their own nuclear deterrents."
Former US President Jimmy Carter has said that Israel has 150 nuclear weapons.
Recently the US accused Syria of building a nuclear reactor "not intended for peaceful purposes". This site was bombed by the Israelis last September.
In addition, the existing nuclear-armed countries are also modernising their weapons. The UK is upgrading Trident, the US is planning the so-called Reliable Replacement Warhead and the Russian and Chinese have their plans.
All this adds to the sense that nuclear non-proliferation remains a key world issue and one that is straining at its belt.
And it will only get more difficult if the Iran question is not resolved.
But that does not seem likely in the near future.