The US and Iran are gearing up for their first high-level talks on Tehran's nuclear programme.
One of the state department's most senior officials, William Burns, will be joined in Geneva by envoys from the EU, China, France, Germany and Russia.
They are expected to discuss incentives for Iran to suspend its uranium and plutonium activities with the country's top nuclear negotiator, Saeed Jalili.
The US attendance is being seen as a major shift in policy.
In 2002, President George W Bush famously named Iran as one of the countries that formed the "axis of evil".