"We are trying and we are determined to cooperate (with the International Atomic Energy Agency)," Kamal Kharazi told ABC television on Sunday.
"The problem is that United States administration asked us to stop enrichment activities in Iran. While it is legal ... and nothing is wrong as long as it is under the auspices of the IAEA and the inspection regime," he said.
Highly enriched uranium can be used to make nuclear weapons, which Washington accuses Tehran of planning to do.
Kharazi said Iran was ready to sign a new protocol with the IAEA to ease US concerns.
"If we sign the additional protocol, we want to make sure that we can continue with enrichment facilities to produce fuel needed for our power plants," he said.
"We want to make sure that this is enough and is going to solve our problems and remove all suspicions."
Powell not satisfied
Colin Powell plays the unproven WMD card
US Secretary of State Colin Powell told ABC that Iran's signing the protocol "in and of itself isn't enough." "We have to have all questions with respect to their nuclear weapons programs answered," he said.
"Over the past year, the evidence that has come forward, that is now before the IAEA, has made it clear to the world that there is something going on in Iran with respect to nuclear weapons development that goes beyond their nuclear power industry."
The IAEA has given Iran until 31 October to prove it has no secret nuclear weapons programme, as the United States alleges.
It has also called on the country to cease uranium enrichment, amid the discovery by IAEA inspectors in Iran of traces of highly enriched uranium - traces that Iran insists were imported along with equipment from overseas.
Putin and Bush met this week to
discuss Iran among other issues
US President George Bush has called on Tehran to be forthcoming with information on its nuclear programmes and said "it is in our national interests to make sure that Iran does not develop a nuclear weapon."
The US is also pressing fellow nuclear power Russia not to sign an accord that would allow Iran's first nuclear power plant – which is being built by Russia – to go online.
Inspectors are expected to arrive in Tehran on Thursday for further inspections and talks with Iranian officials.