The will of the European Union and the rest of the international community is "very, very clear", MacShane told reporters as he arrived for a meeting of EU foreign ministers.
"We want Iran to state unequivocally that there are no nuclear weapon possibilities that could be developed as a result of any nuclear programme in Iran," he said.
"We want Iran to cooperate fully with the international inspection agencies," added MacShane, standing in for Foreign Secretary Jack Straw at the EU meeting.
"That's what the entire international community wants from Iran and I hope Iran is listening to that common and uniform demand from everybody in the international community."
Iran on Sunday signalled its willingness to comply with the demands of the UN's International Atomic Energy Agency, but vowed to continue its uranium enrichment programme.
"We are trying and we are determined to cooperate" with the IAEA, Iranian Foreign Minister Kamal Kharazi told ABC television in the United States.
The IAEA has given Iran until October 31 to answer all its questions concerning allegations that it is seeking to develop atomic weapons.
The EU foreign ministers are expected to renew their demands for Tehran to sign an additional protocol to the nuclear Non-Proliferation Treaty that would allow IAEA inspectors to descend on its nuclear sites without warning.
The EU has warned that, without credible guarantees over the protocol, it will review its economic ties with Iran.