Iran and the P5+1 group - the US, UK, Russia, China, and France plus Germany - sealed a six-month Joint Plan of Action in November last year. Under the plan, Iran agreed to curb parts of its nuclear programme for six months in exchange for modest relief from international sanctions.
"The United States and the rest of our P5+1 partners will also take steps, in response to Iran fulfilling its commitments, to begin providing some limited and targeted relief," Kerry said.
Following the agreement in Geneva, in a statement Kerry said that Iran will voluntarily take immediate and important steps between now and January 20 to halt the progress of its nuclear programme.
Iran will also continue to take steps throughout the six months to live up to its commitments, such as rendering the entire stockpile of its 20 per cent enriched uranium unusable for further enrichment.
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Noting that while implementation is an important step, he said the next phase poses a far greater challenge: negotiating a comprehensive agreement that resolves outstanding concerns about the peaceful nature of Iran's nuclear programme.
Reiterating that the US would not allow Iran to acquire nuclear weapons, Kerry said the Obama Administration has been clear that diplomacy is its preferred path because other options carry much greater costs and risks and are less likely to provide a lasting solution.
"We are clear-eyed about the even greater challenges we all face in negotiating a comprehensive agreement. These negotiations will be very difficult, but they represent the best chance we have to resolve this critical national security issue peacefully, and durably," he noted.
Western countries have long suspected Iran of pursuing a nuclear weapons capability. But Iran has denied the charges.