"What's going to be important to us is that Iran respond fully and comply fully with all the requirements of the International Atomic Energy Agency," State Department spokesman Richard Boucher said.
His comments came amid signs that Iran is gradually moving to fulfill a series of steps the IAEA called for last month and set an October 31 deadline for meeting, including moving toward agreeing to spot inspections of its nuclear facilities under an additional protocol to the nuclear Non-Proliferation Treaty.
"The (IAEA) board of directors was quite specific in the long list of questions that they needed to answer and actions that they needed to take, including by signing and then implementing the additional protocol," Boucher said.
"We certainly look to Iran to do all of that and I wouldn't have any comment if some partial effort had been made," he said.
The United States accuses Iran of pursuing clandestine nuclear weapons development under the cover of its civilian atomic energy program, a charge Tehran has vehemenly denied.
Pushed by the United States, the IAEA on September 12 gave Iran until the end of this month to guarantee it is not developing and will not develop nuclear weapons.
Failure by Iran to meet the deadline could see it being declared in violation of the non-proliferation treaty and the matter being passed to the UN Security Council, which could impose sanctions as a result.
Iran reacted angrily to the demands at first but initial opposition to meeting the requirements appears to have subsided.
Friday, an IAEA team began a crucial round of inspections in Iran after reaching an accord with Iranian officials on a list of sites to visit.
However, it was not clear whether Iran has agreed to open up for visits all of the sites demanded by the IAEA team, which arrived in Tehran last week for a mission the agency's chief Mohamed ElBaradei has described as "decisive".
In addition, Iran said it had started handing over lists of parts imported for its nuclear program to the inspectors.
The IAEA has asked Iran to produce a detailed list of its nuclear-related equipment, notably parts used in centrifuges for uranium enrichment, in order to resolve what have been described as "outstanding issues."