The U.N. atomic watchdog has received new information regarding allegations that Iran may be seeking to develop a nuclear-armed missile, the agency said in a report voicing deepening concern about the issue.
The International Atomic Energy Agency has been investigating the Islamic republic's disputed atomic drive for a number of years, with a range of issues still unresolved, among them allegations that Iran had undertaken studies to build a nuclear payload for a missile.
In a restricted new report the IAEA said Iran was still refusing "to discuss a number of outstanding issues related to possible military dimensions to its nuclear work."
It also underlined Iran's determination to press ahead with sensitive atomic activity despite four rounds of U.N. sanctions since 2006, saying the country had informed the IAEA it would soon start operating a second uranium enrichment plant.
The Islamic Republic had also told the Vienna-based U.N. body of plans to step up efforts to introduce more advanced machines used to enrich uranium, which can have both civilian and military purposes, the report said.
In the 12-page report, the IAEA said Iran's stockpile of low-enriched uranium in the main branch of its Natanz uranium enrichment plant had now reached 3,606 kilograms (7,933 pounds).
Uranium enrichment is the most controversial part of Iran's nuclear activities because it can be used not only to generate nuclear fuel, but also to produce the fissile material for a nuclear bomb.
The report looked likely to add to Western suspicions that Iran is secretly bent on building a nuclear weapons capability from its enrichment program, which Tehran denies.
It may also provide the United States and allies with additional arguments for further tightening sanctions on Iran, after talks in December and January failed to make any progress towards resolving the dispute.
The IAEA report said it remained concerned about possible current activity in Iran to design a nuclear payload.
"Iran is not engaging with the agency in substance on issues concerning the allegation that Iran is developing a nuclear payload for its missile program," it said.
The report said that based on an analysis of "additional information which has come to its attention since August 2008, including new information recently received, there are further concerns which the agency ... needs to clarify with Iran."
Allegations "totally fabricated"
Iran's ambassador to the IAEA, Ali Asghar Soltanieh, told Reuters that allegations of military aspects to Iran's nuclear program were "totally fabricated".
Enriched uranium can be used to fuel nuclear power plants, which is Iran's stated aim, or provide material for bombs if processed much further.
In a surprise development, the report said Iran had said it "would have to unload fuel assemblies" from the core of the Russian-built Bushehr reactor, which Iranian officials have previously said would soon start generating electricity.
Iran did not give a reason for its move, which was announced a month after Russia said NATO should investigate a computer virus attack on Bushehr last year, saying the incident could have triggered a nuclear disaster on the scale of Chernobyl.
Last week, state media quoted Iranian Foreign Minister Ali Akbar Salehi as saying that 1,000 megawatt reactor on Iran's Gulf coast was undergoing tests and that "everything is ready to produce electricity in the near future".
But a senior Iranian atomic energy official said earlier this month the country should investigate claims that the Stuxnet computer worm, which security analysts suspect targeted Iran's nuclear program,, had caused major harm to Bushehr.
Speaking after a Russian official warned of a "new Chernobyl", the official, Mohammad Ahmadian, said reports of major damage to Bushehr were a malicious campaign by countries hostile to Tehran's nuclear program, but that they should be looked into in any case.
Security experts say Stuxnet may have been a state-sponsored attack on Iran's nuclear program and may have originated in the United States or Israel.
Despite a brief halt of enrichment work in November, Iran's total output of low-enriched uranium rose to reach a total of 3.61 tons, from 3.18 tons at the end of October, suggesting steady work despite technical woes and possible cyber sabotage.
Experts say that amount could be enough for two bombs if refined much further.
In a further sign that Tehran has no intention of bowing to demands to halt such activity, the report said Iran had told the IAEA earlier this week it planned to begin feeding nuclear material at its second enrichment facility "by this summer".
In September 2009, Iran revealed the existence of the site, Fordow, being built inside a mountain bunker near the central city of Qom after keeping it secret for years.
Iran had also said it planned to install two new centrifuge cascades in a R&D facility at its main enrichment plant at Natanz with more modern machines than the IR-1 model now in use, which is based on a 1970s design and prone to breakdowns.
"They should have a significantly higher enrichment output and a lower failure rate than the IR-1 centrifuge," the Institute for Science and International Security, a Washington-based think-tank, said in an analysis.
Iran to remove fuel
Iran will remove the fuel from the reactor of a Russian-built nuclear power plant in the southern city of Bushehr, a top official said on Saturday, citing technical advice from Moscow.
The plant, which has seen a roller-coaster ride since its construction began in the 1970s, was scheduled to generate electricity from April 9, and the latest development signals a likely delay in achieving that aim.
"Based on the recommendation of Russia, which is in charge of completing the Bushehr atomic power plant, the fuel inside the reactor core will be taken out for a while to conduct some experiments and technical work," Iran's envoy to the UN atomic watchdog, Ali Asghar Soltanieh, told the ISNA news agency.
"After the experiments, it will again be installed in the core of the reactor." He did not specify when the experiments would be completed.
Iran had started loading the fuel into the plant on August 21, which Moscow at that time said was the "physical launch" of the facility.
In January, Iran's former atomic chief Ali Akbar Salehi said the plant would be ready to generate electricity on April 9 after operations began on November 27.
The decision to remove the fuel, also supplied by Russia, is the latest development in the more than three-decade old history of the plant, which was first launched by the U.S.-backed shah using contractors from German company Siemens.
But it was shelved when the shah was ousted in the Islamic revolution of 1979 and it lay unfinished through the 1980s as Iran battled internal opposition and a devastating eight-year war with Iraq.
It was revived in the late 1980s after current supreme leader Ali Khamenei succeeded revolutionary leader Ayatollah Ruhollah Khomeini.
In the early 1990s, Iran sought help for the project after being turned away by Siemens over nuclear proliferation concerns.
In 1994, Russia agreed to complete the plant and provide the fuel, with the supply deal committing Iran to returning the spent fuel.
A deal was finally signed in January 1995 after 18 months of negotiations and preliminary accords.
That was just the start of a spate of delays and setbacks, as the Russian contractor was repeatedly forced to postpone completion.
In 2007, Russian contractor Atomstroiexport even accused Iran of falling behind in its payments, further jeopardising the project's completion.
But finally on August 21 last year, Russian and Iranian engineers started loading the facility with the fuel, a move undertaken despite Moscow hardening its stance against Tehran's nuclear program by voting for a new sanctions resolution at the UN Security Council.