"Iran is still bound by its commitments," foreign ministry spokesman Hamid Reza Asefi told reporters.
"There is no sign from our side that we will question our cooperation, but the agency should not create an atmosphere that pushes our leadership to doubt this cooperation," he cautioned.
His comments came two weeks before the Vienna-based International Atomic Energy Agency (IAEA) is due to again examine Iran's dossier amid ongoing suspicions that Iran is using a bid to generate nuclear power as a cover for secret weapons development.
Iran insists that its nuclear programme is purely peaceful, and last year signed an additional protocol to the nuclear Non-Proliferation Treatyallowing tougher IAEA inspections.
The country has also suspended uranium enrichment, amid widespread international concern that it was close to producing weapons-grade material.
"We have shown the greatest cooperation with inspectors and have placed no restrictions on their work. We have nothing to hide," Asefi said, dismissing reports from diplomats that IAEA teams have been prevented from visiting some military sites.
IAEA chief Mohamed ElBaradei said last week that Iran's cooperation with the agency had been insufficient, but added that he had not drawn any conclusions over the nature of the country's nuclear programme.
If Iran comes under renewed criticism on June 14 and more doubts emerge over its cooperation, the IAEA's board could refer the matter to the UN Security Council, which in turn could choose to impose sanctions.
Asefi said Iran was still hoping that during its June meeting the IAEA would examine the Islamic republic's case "without politicising it and so that the dossier can be closed as soon as possible".
"There is pressure on the agency," he added, referring to lobbying from the United States, "but if the (IAEA) board of governors work diligently, there is no reason why the dossier should not be closed."
Although Iran has been urging the IAEA to pull Iran's case off the top of its agenda, President Mohammad Khatami has acknowledged that no such step will be taken during the June meeting.
The spokesman also called on European states to counter US pressure, reminding them of the commitment of Britain, France and Germany last year to offer technical support to Iran if it bows to IAEA demands.
"If the Europeans do not keep their promises, we see no reason to continue cooperating with them," he warned.
On Thursday, President Khatami repeated warnings Iran could resume uranium enrichment if the UN watchdog gives in to pressure from the United States. However Asefi said the president's comments "do not signify Iran will disengage from the NPT."