Iran has expanded its Natanz nuclear site, but slowed uranium stockpiling, according to the International Atomic Energy Agency (IAEA). Tehran's stockpile of 20% enrichment uranium reached 167 kilograms this month after production was resumed in December.
A Thursday report from the IAEA says that Iran began converting higher-grade enriched uranium for fuel production in December, and has since fed 28.3 kilograms of the material for this purpose.
The February levels represented a rise of about 18-19 kilograms since the November report, a diplomat told Reuters.
However, the growth is still a notable slowdown from the previous three-month period when the stockpile jumped by nearly 50 per cent after Iran halted conversion.
The IAEA also said 180 IR-2m centrifuges and empty centrifuge casings had been hooked up at the plant near the town of Natanz.
If operated successfully, such machines could allow Iran to speed up its accumulation of material that western countries fear could be used to devise a nuclear weapon.
Iran has almost completed installation of cooling and moderator circuit piping in the heavy water plant near the town of Arak, according to the report.
Nuclear analysts say this type of reactor could yield plutonium for nuclear arms if the spent fuel is reprocessed. However, Iran says it “does not have reprocessing activities.”
The report also says that "extensive" activities at Iran's Parchin military facility would seriously undermine an IAEA investigation to determine whether explosives research relevant to nuclear weapons was done there.
About 240-250 kilograms of 20 per cent enriched uranium is needed for one atomic bomb if refined to a high degree.
Iran has continuously maintained that its nuclear program is for purely peaceful purposes and is set to meet growing energy and cancer treatment needs. Iranian Supreme Leader Ayatollah Ali Khamenei said earlier this week that Tehran has no intention of developing nuclear weapons.
"We believe nuclear arms must be eliminated, and we don't want to build nuclear arms," Khamenei said, adding, however, that if Iran did want to create a nuclear warhead, no country could prevent it from doing so.
In his speech, Khamenei accused the US of fraud, saying that Washington is calling for the elimination of nuclear weapons while continuing to produce them.
The news comes ahead of next week's talks between Tehran and world powers in Kazakhstan. UN Security Council members from the United States, Britain, China, Russia, and France, plus Germany, will be present at the meeting.
The United States said on Thursday that Iran's installation of advanced centrifuges would be "yet another provocative step."
"The installation of new advanced centrifuges would be a further escalation and a continuing violation of Iran's [UN] obligations," U.S. State Department spokeswoman Victoria Nuland said.
White House spokesman Jay Carney said the window for diplomacy with Iran remains open "but that window will not remain open indefinitely." He said that Tehran should come to the February 26 talks prepared for "substantive" discussions.
France echoed Washington's sentiments on Thursday. "We hope that Iran will attend this meeting with a constructive spirit and will be ready to discuss, in detail and with a renewed perspective, aspects of its nuclear program that remain to be clarified...we want a true exchange, leading to concrete results," French foreign ministry deputy spokesman, Vincent Floreani, said in a statement.
He confirmed that world powers would make a "substantial" new offer to Iran, in an effort to resolve the dispute over its nuclear program.
"We will make a new offer that will contain significant new elements," Floreani said.
Israel has claimed that Iran is “closer than ever” to the ability to build a nuclear bomb. "Iran is closer than ever today to obtaining enriched material for a nuclear bomb," read a statement, issued by the office of the Prime Minister Benjamin Netanyahu, which described the report as “severe.” The statement noted that "preventing nuclear arms from Iran will be the first topic Prime Minister Benjamin Netanyahu will discuss with US President Barack Obama," who is expected in Israel in March.
Iran has been facing economic sanctions from western countries because of its failure to halt certain aspects of its uranium enrichment program. Tehran says it is enriching uranium only to make reactor fuel and for scientific and medical purposes.