Representatives of Iran met in Almaty, Kazakhstan, with counterparts from the United States, France, Britain, Germany, China and Russia. Ashton described the talks as "long and intensive" and said they produced no movement, CNN reported.
"It became clear that the positions of (the world powers) and Iran remain far apart on the substance," Ashton said. "We therefore agreed all sides will go back to their capitals to evaluate where we stand on the process."
Iran says its nuclear program is intended exclusively to generate power but the countries involved in the talks -- the five veto powers on the United Nations Security Council plus Germany -- say Iran needs to be more transparent about its nuclear facilities.
The group hoped Iran would respond to a plan presented at a meeting in February in Almaty, CNN said. Instead, Iran brought in its own plan that Ali Baghery, the head of its delegation, said is aimed at establishing "a new bedrock of cooperation."
No date or place has been announced for further negotiations.