Senior official William Burns will sit at the same table as Iran's negotiator
news.bbc.co.uk/2/hi/middle_east/7513666.stm (external - login to view)
Iran's top nuclear negotiator has voiced guarded optimism about talks attended by the US this weekend.
Saeed Jalili was speaking as he left Tehran for Geneva for the meeting on Iran's controversial nuclear programme with the EU foreign policy chief.
The attendance for the first time by a top US diplomat at such a meeting is being seen as a major policy shift.
"If it is with a constructive approach... for sure we will have constructive talks," Mr Jalili said.
Mr Jalili will represent Iran at the talks with Javier Solana to discuss the package of incentives offered by world powers to Tehran as well as a package which Iran has presented itself.
"In these talks we will discuss the common points of the two packages and also both sides' ideas on continuing the talks," he said in remarks quoted by the official Iranian news agency.
Speaking in Ankara, Iranian Foreign Minister Manouchehr Mottaki welcomed "a new positive approach" after talks with his Turkish counterpart Ali Babacan.
"If the negotiations continue in this way, I hope there will be a positive outcome," he said.
Saturday's talks will aim to find out how Iran will respond to the West's offer of economic incentives if Tehran suspends its uranium enrichment programme.
Iran denies any nuclear weapons plans, but is defying UN Security Council demands to halt uranium enrichment.
Mr Mottaki did not confirm Thursday's media reports that the US was thinking of establishing an interests section in Tehran and launching direct air links, but he said he was open to such ideas.
"In my opinion, talks and a deal on an American bureau in Iran and direct flights between Iran and the United States is possible," he said.
It would be the first such link between the US and Iran since the Islamic Revolution and the US hostage crisis nearly 30 years ago.
The latest moves appear to have eased tension between the two foes, which had been escalated by Iranian missile tests last week, war games by Israel - the US main regional ally - and a series of threats and counter-threats.
In the past, the Bush administration has insisted that no talks would be held with Iran until it suspends its uranium enrichment programme which could be harnessed to produce weapons.
The Bush administration says the presence of State Department number three William Burns is designed to demonstrate the West's unity and to reiterate that the terms of negotiations remain the same.
The US is among six world powers which have offered Iran negotiations on a package of incentives, including direct contact and dialogue.
Formal contacts between the US and Iran are very rare, though the two countries held three rounds of talks in 2007 over Iraq.