BRUSSELS - The British, French and German foreign ministers are due to meet Iranian nuclear negotiators in Lausanne on Saturday, European diplomatic sources told Reuters, adding that a final decision would depend on talks among officials on Friday.

It was not immediately clear if the foreign ministers would be joined by the Russian, US and Chinese counterparts who are part of a process aimed at ending a confrontation over Tehran's nuclear programme. The sources spoke after the French, German and British leaders met the EU foreign policy chief in Brussels.

"The meeting today on Iran was useful to consolidate a European line," one diplomatic source told Reuters after European Commission Vice President Federica Mogherini met British Prime Minister David Cameron, French President Francois Hollande and German Chancellor Angela Merkel for about 40 minutes before a second day of wider talks at an EU summit.

"A will to find a good deal has been confirmed by all participants," the source said. "The target is to reach a deal as soon as possible, bearing in mind that June is the deadline."

A second source described Friday's meeting in Brussels as a "useful informal session on coordination and consultation".

The talks came after a senior European Union negotiator at talks in Switzerland said that the six world powers are unlikely to reach a framework agreement with Iran on its nuclear work in the coming days as the sides are still far apart on key issues.