Negotiations aimed at resolving the stand-off over Iran's nuclear programme ended in deadlock yesterday, raising fears that the regime could accelerate its nuclear weapons development and potentially spark a crisis in the Middle East.
Ms Ashton, the European Union's foreign policy chief, said the talks hit a stalemate after Iran laid down preconditions. The conditions, she said, related to its uranium enrichment.
Iran also called for an end to sanctions imposed by the United Nations in 2006, which were tightened last summer.
William Hague, Britain's Foreign Secretary, said Iran's "insistence on preconditions that were clearly unrealistic is extremely disappointing".
Saeed Jalili, Iran's chief nuclear negotiator, denied it had set preconditions, but said there were "necessities that need to precede any meaningful talks".
Iran and a six-nation group known as the P5+1 -- the United States, Britain, Russia, China, France, plus Germany -- began negotiations in Istanbul on Friday, 15 months after earlier negotiations failed. British and French diplomatic sources said the two sides failed to find common ground on three issues.
First, Iran demanded an end to sanctions before further discussions. The group said the sanctions could only be lifted if Iran met UN demands to make its nuclear programme transparent.
Iran also claimed it had the right to enrich uranium under the Nuclear Non-Proliferation Treaty. Finally, Iran called for talks on tightening the treaty -- an appeal for action on Israel's nuclear arsenal. Both sides said they were open to further discussions, but did not set a date.
Diplomats warned the stalemate could strengthen the hands of hardliners who want military strikes on Iran's nuclear facilities.