The International Atomic Energy Agency said in its latest report that it wasn't able to verify the intent of Iran's nuclear program. The agency said it was concerned about new centrifuges installed at the Natanz enrichment plant and the lack of access to the Parchin military complex.
Joseph Macmanus, U.S. envoy to the IAEA, said Washington shared the IAEA's concerns. On Natanz, he said he questioned Iran's need for more centrifuges "given the absence of any immediate need to do so for peaceful nuclear purposes."
Iran says it has the right to nuclear research as a signatory to the Nuclear Non-proliferation Treaty. Iran's representatives this year said there was no nuclear activity at Parchin, though Macmanus said recent satellite imagery of the site suggested otherwise.
"Iran has had more than enough time to explain its activities and offer the cooperation that one would expect of a country seeking a legitimate civil nuclear energy program," he said.
Iran said it saw a change in tone from Western powers during recent nuclear negotiations in Kazakhstan. Another round of talks is scheduled for April.