There is still room for talks with Tehran over its disputed nuclear programme but the run-up to Iranian presidential elections in June complicates the situation, a Western diplomat said Monday.

"There is enough substance for these negotiations to continue," said the diplomat after the latest round of talks between world powers and Iran failed to reach an accord despite early hopes of progress.

"I would not expect a breakdown," the diplomat added.

The sticking point at the talks in the Kazakh capital Almaty were demands that Tehran curb its uranium enrichment activities to levels in keeping with civilian needs in return for the easing of Western sanctions which are biting ever deeper.

Iran failed to give "a concrete, comprehensive and complete response" to the offer on the table despite earlier statements of good will, one official said after the talks ended Saturday.

The Western diplomat said the talks seemed to make no progress, despite upbeat Iranian comments about an earlier round in Almaty, because of the election backdrop.

"The internal power struggle has an impact on negotiations," the diplomat said. "Maybe it will be easier once we know who the presidential candidates are."

"The problem has always been one of trust," said the diplomat who asked not to be named.

Britain, France, the United States, Russia and China -- the five permanent UN Security Council members plus Germany known collectively as the P5+1 -- suspect Iran wants to build an atomic bomb under the guise of its civilian nuclear energy programme.

That view has been supported by Iran's refusal to fully cooperate with UN nuclear inspectors and its failure to disclose in a timely manner the existence of a mountain bunker called Fordo that enriches uranium to high levels just a few technical steps from weapons-grade material.

EU foreign affairs head Catherin Ashton, who chairs the P5+1 talks with Iran, said Saturday she would contact Tehran within days to find a way to move beyond Almaty and agree on a new meeting.