The top US diplomat, who arrived in London for talks on Friday on Iran, the Middle East peace process and Kosovo, insisted on the need to "fully" implement United Nations sanctions levied on Tehran.
"We will take a look again at what we have offered the Iranians," she told journalists on the plane en route to Britain.
"But I just want to say I don't see any evidence that the Iranians appear to be interested in that track," she said, adding that she did not expect any notable results from Friday's meeting.
Rice will join with her counterparts from Britain, Germany, France, Russia and China in the talks on Iran, in which the West has adopted a carrot-and-stick approach to discussions with the Islamic Republic over its controversial nuclear programme.
They have offered technical, political and economic rewards to Tehran for suspending its nuclear programme, which the West says is for military purposes despite Iran's vehement denials.
But those offers have never been made public and official documents obtained by the media suggest the offer was vague. Several countries, including Russia, say those proposals should be developed.
At the same time, the UN Security Council has adopted three resolutions imposing sanctions on Iran for its refusal to suspend its uranium enrichment activities.
Rice has not been keen on offering new incentives to Tehran, describing the offer already made as "very generous".
"If there are things that can be done to improve the chances that the Iranians will do what they should have done and ought to do, fine," she said. "Let's look at it."
"I don't think the problem is the package. I think the problem is Iranian will."
She added: "I also believe that we have got to intensify our efforts on the UN Security Council … I believe that there is plenty in the Security Council resolutions that if fully implemented, fully executed, fully used, will increase the pressure on Iran."
Rice insisted she was not "accusing anyone of bad faith", but was instead arguing for the proper application of the sanctions.
