Rice, speaking to reporters after talks with Italian Foreign Minister Massimo D'Alema, added that the United States is still expecting a clear answer on the proposal, and hopes Iran will take what she called the right path.
"Certainly we have heard some positive statements from the Iranians," she said in the most optimistic public US assessment to date.
Earlier on Friday, Iranian President Mahmoud Ahmadinejad welcomed a proposal by world powers to defuse a standoff over Tehran's nuclear activity as a positive step but gave no sign when an answer would come.
Ahmadinejad, markedly more upbeat about the proposal on a trip abroad than he has been at home, said Iran was examining the offer of incentives for Tehran to stop enriching uranium, a process that could eventually yield atomic bombs.
He also warned Iran would not be concerned by possible sanctions if it rejects the June 6 offer.
US Energy Secretary Sam Bodman called "encouraging" the Iranian president's comments.
Ahmadinejad did not say when Tehran would officially respond to the package offered by six major powers under which Iran would get trade and technology benefits if it halts uranium enrichment work.
The offer from the United States, Britain, France, Germany, China and Russia was delivered to Tehran earlier this month.
The West is worried Iran is pursing the uranium program to eventually build an atomic bomb, even though Tehran insists it is seeking nuclear power only to boost electricity supplies.
If Iran rejects the package, the United States is expected to push hard for sanctions against Iran, the world's fourth largest oil exporter, at the UN Security Council.