"We are trying and we are determined to cooperate" with the International Atomic Energy Agency, Kharazi told ABC television.
"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 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."
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 October 31 to answer all its questions concerning allegations that it is seeking to develop atomic weapons.
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.
US President George W. Bush and Russian President Putin on Saturday discussed Iran, with the Russian leader saying that a "clear but respectful signal" should be sent to Tehran about the need to cooperate with the IAEA over its nuclear facilities.
Bush, for his part, called on Tehran to come clean on its nuclear programmes and said it was "in our national interests to make sure that Iran does not develop a nuclear weapon."
Moscow is building the Islamic state's first nuclear power reactor, but says it will not begin delivering nuclear fuel needed to operate the plant until Tehran signs a deal pledging to return the spent material to Russia.
Under pressure from the United States and Israel, Russia has made the return of the spent fuel a key condition for concluding the 800 million dollar (715 million euro) project.
But Kharazi said he believed it was possible for the United States to develop better relations with Iran, which was one of the three nations Bush named in his "axis of evil."
"It has been always possible," Kharazi said. "What is lacking here is that political will."
"To start any dialogue between Iran and the United States, this has to be based on mutual respect and equal footing. Otherwise, there's no meaning to have such a dialogue," he said.
"We don't want the United States to interfere in our internal affairs. We want the United States to take gestures to prove that it's sincere in its call for a dialogue.