The International Atomic Energy Agency (IAEA), in a May 26 report, also said Tehran should provide more information on its missile-related work.
Iran's Foreign Ministry spokesman said Tehran believed the U.N. agency could have submitted a better report had it not been for the "continuing pressures of one or two known countries," in a clear reference to Tehran's Western foes.
The United States accuses the Islamic Republic of seeking to develop nuclear arms. Iran denies the charge but its refusal to suspend sensitive nuclear work has prompted three rounds of U.N. sanctions since 2006.
"In regard to this report, we of course had more expectations from the agency," spokesman Mohammad Ali Hosseini told a news conference, a day before the IAEA's board of governors begin a June 2-6 meeting in Vienna.
He added: "The trend of cooperation … should continue in a way that, as Dr Larijani pointed out, the parliament and the Islamic Republic of Iran would not be compelled to review the going trend of the cooperation and adopt new limitations."
He was referring to Iran's new parliament speaker Ali Larijani, who on Wednesday said the current levels of cooperation with the IAEA were in jeopardy if major powers continued to "kick around" Iran's disputed nuclear case.
Hosseini did not elaborate under what circumstances and in what way Iran might limit cooperation with the IAEA.
Iran in 2006 ended voluntary implementation of the Additional Protocol to the Non-proliferation Treaty that allowed for short notice IAEA inspections of its nuclear sites, after being referred to the U.N. Security Council.
U.S. Secretary of State Condoleezza Rice said on Wednesday Iran had much to explain about the latest IAEA report.
But Larijani, in comments after he was elected speaker of parliament on Sunday, accused U.S. and Israeli intelligence services of misleading the IAEA and said this could force Iran to "choose a different path", state television reported.
Earlier on Sunday in Singapore, French Defence Minister Herve Morin said Iran should open its nuclear installations to international scrutiny to clear suspicions about its ambitions.
The IAEA has been pressing Tehran to provide answers to Western intelligence accusations that it covertly studied how to design atomic bombs. Iran has rejected the intelligence as baseless, forged or irrelevant.
World powers have prepared an enhanced package of economic and other incentives for Iran if it suspends its most sensitive nuclear work, something Tehran has consistently refused to do.
(Reporting by Hossein Jaseb and Hashem Kalantari; Writing by Fredrik Dahl; Editing by Elizabeth Piper)
