Iran has urged the US to offer it further incentives to resolve the dispute over its nuclear programme.
Tehran says it is not seeking to acquire nuclear weapons
The US should unblock frozen Iranian assets, lift sanctions and stop "hostile measures", a senior Iranian negotiator told BBC News.
President George W Bush announced a major change in US policy on Friday.
He said the US would back European talks to resolve the stand-off and, unlike before, was prepared to extend economic incentives to Tehran.
These included the lifting of a decade-long block on Iran's membership of the World Trade Organization (WTO), and objections to Tehran obtaining parts for commercial planes.
But Iran rejected the offer as "insignificant" and vowed to exercise its "legitimate right" to use nuclear technology for peaceful purposes.
Washington accuses Iran of using its nuclear enrichment programme as a cover for developing nuclear weapons.
Tehran denies seeking nuclear weapons, but has suspended uranium enrichment after negotiations with France, Germany and the UK.
The US and European Union want that move made permanent, and have threatened to seek United Nations sanctions if Iran does not comply.
More confidence-building measures
Hossein Mousavian, the secretary of the foreign relations committee of the Supreme National Security Council, told the BBC the US offer to allow Iranian membership of the WTO and sales of aircraft spare parts did not amount to real concessions.
Mr Mousavian said, however, that Iran would embrace with open arms confidence-building measures and objective guarantees to prove that it was not seeking weapons of mass destruction.
But he added that Iran remained determined to produce at least part of its nuclear fuel for power plants and he said if that was accepted, then the debate over economic and security concessions could become serious