Iran's chief nuclear negotiator Ali Larijani and European Union foreign policy chief Javier Solana will meet on May 31st for a new round of talks on Tehran's nuclear programme.
Mr Larijani and Mr Solana last met on April 25-26 in the Turkish capital Ankara to discuss Iran's nuclear row with the west.
The IRNA news agency said today they agreed to meet again during a telephone discussion in which they emphasised the need for a "logical and legal solution through diplomatic means".
It did not say where the meeting would take place.
A spokeswoman for Mr Solana said she could not confirm a date or venue for the next round of talks but the EU foreign policy chief told a reporter yesterday he expected it would be around the end of the month.
Solana made clear in an interview with a German newspaper that any talks with Iran would be difficult and take time to find a solution.
"Our dispute over the Iranian nuclear programme cannot be resolved in hours, or days or months. It will probably take years," he told the Frankfurter Allgemeine Zeitungaccording to extracts of an interview to be published in full tomorrow.
Iran is embroiled in a deepening standoff with major powers over its atomic ambitions, which the west fears are aimed at making nuclear weapons. Tehran says it only wants to produce electricity.
The United Nations has imposed two sets of sanctions on Iran since December over its refusal to freeze enrichment - a process that can be used to make atomic warheads.
US officials have warned of a third, tougher resolution if Tehran does not halt such work, but Iranian leaders have repeatedly said they will not bow to such pressure.
Earlier today, the director of the United Nations atomic watchdog agency, Mohamed ElBaradei, said Iran's progress in enriching uranium has rendered unrealistic world powers' quest to prevent Tehran from gaining nuclear expertise.
"We believe they pretty much have the knowledge about how to enrich. From now on, it is simply a question of perfecting that knowledge. People will not like to hear it, but that's a fact," Mr ElBaradei said.
Iran has ramped up its programme from the research level since the start of 2007, installing more than 1,600 enrichment centrifuges, divided into 10 fuel-cycle "cascades", or networks, in an underground complex by the start of May, diplomats said.
Tehran has been hooking up one cascade every week or so, they said, and intends to have 3,000 operational by next month to lay a foundation for "industrial-scale" enrichment.
In Washington, State Department spokesman Tom Casey said it was clear Iran continued to defy the international community.
"For us, Iran is increasingly isolated and certainly from our perspective the only way to get them to change their behaviour is to have sustained pressure with the offer of negotiations," Mr Casey said.
He said there was still time for diplomacy to work, but added: "I certainly expect that if Iran does not change its position and come into compliance that there will be additional Security Council resolutions and Iran will face additional sanctions."