By Mark Heinrich
UN official says Islamic Republic merely providing flat denials but no access.
Iran has blocked a UN inquiry into whether it researched ways to make a nuclear bomb, the UN nuclear watchdog said on Monday, and Britain said it would push hard for tougher sanctions against Tehran.
A confidential IAEA report said Iran had raised the number of centrifuges enriching uranium by 500 to 3,820 since May and was testing an advanced model able to refine nuclear fuel 2-3 times faster, in defiance of UN resolutions.
But a senior UN official familiar with the International Atomic Energy Agency findings said Iran seemed at least two years away from enriching enough uranium for an atomic weapon, if it eventually chose to do so.
Iran denies it nuclear work is aimed at developing a bomb.
"On the issue of possible military dimensions to Iran's nuclear programme, we have arrived at a gridlock. Without Iran's assistance and cooperation, we cannot move forward," said a second senior UN official.
Iran blamed the IAEA for the impasse. A senior Iranian official, who declined to be named, called on the IAEA to change its approach and work in a "legal and logical" manner.
Britain accused Iran of showing "contempt for the IAEA by continuing to refuse to respond" to IAEA Director Mohamed ElBaradei's serious concerns about possible covert bomb work.
"We will therefore push hard for further UN sanctions in the coming weeks," a British Foreign Office statement said.
Iran has withstood limited sanctions imposed so far and may count on Russia, at odds with Western powers over Georgia, to hold up harsh action by the UN Security Council, analysts say.
The report will be debated by the IAEA's 35-nation board of governors at a meeting starting on Sept 22, with the possibility that Western powers might seek a resolution against Iran.
Iran had stockpiled 480 kg of low-enriched uranium so far, the report by the Vienna-based IAEA said.
It would need 1,700 kg to convert into high-enriched uranium (HEU) for fuelling an atom bomb, said UN officials who spoke on condition of anonymity.
"That would be a significant quantity, one unit of HEU, and would take on the order of two years," said one official.
The report coincided with the announcement by Iran that it was staging air defence exercises in half of its 30 provinces.
Air defence commander Brigadier General Ahmad Mighani "emphasised that the enemies would receive a serious response for any aggression and we would surprise them and make them regretful," the ISNA agency in Tehran reported.
Washington says it wants a diplomatic solution to the nuclear standoff but has not ruled out military action as a last resort. Iran, the No. 4 oil exporter, says its nuclear programme is a peaceful drive for an alternative source of electricity.
In its last report in May, the IAEA said Iran appeared to be withholding information needed to explain intelligence that it had linked projects to process uranium, test high explosives and modify a missile cone in a way suitable for a nuclear warhead.
ElBaradei called on Iran then for "full disclosure" - namely, going beyond flat denials without providing access to sites, documentation or relevant officials for interviews to substantiate their stance.
The report said nothing to that end had been done by Iran, which has acknowledged some of the activity cited but said it was for conventional military purposes only.
"Regrettably the agency has not been able to make any substantial progress on the alleged [weaponisation] studies and other associated key remaining issues which remain of serious concern," the report said.
It said IAEA investigators had stressed to Iran that the intelligence documentation was detailed and consistent enough "that it needs to be taken seriously" by Iran.
But, in a nod to Iranian objections, UN officials said Iran was understandably worried about divulging information it felt could compromise its security as tensions fester between Iran and the United States and Israel.
They said another obstacle was the refusal of Western powers to let the IAEA provide Iran hard copies of the intelligence for perusal. Iran has said it has seen only electronic versions that could easily have been doctored.
Iran's IAEA ambassador, Ali Asghar Soltanieh, told Reuters Tehran would not offer further explanations before "the agency delivers the documents to us". He said IAEA demands went way beyond Iran's legal obligations to cooperate and "we have done more than enough to explain these baseless allegations".
The report said the IAEA was trying to break the deadlock by urging Iran to specify what information was wrong and what was right in its view, but Tehran had not responded so far.
"Iran's refusal to address the [issues] is particularly troubling as it continues to develop the abilities to produce fissile material that could be weaponised into a nuclear bomb," US Ambassador Gregory Schulte told reporters. (Reuters)