TEHERAN (AFP) - A senior Iranian diplomat said on Friday nuclear negotiations in Geneva with world powers were moving closer to an accord after progress was made on the third day, media in Teheran reported.

"To a good degree, we have moved (closer) towards agreement," deputy foreign minister Abbas Araqchi told reporters, according to the Mehr news agency.

But he added, without elaborating, that despite "progress made today, some main issues still remain" in the diplomatic push to end a decade-long dispute over Iran's controversial nuclear drive.

The remarks came as the US State Department announced that Secretary John Kerry would fly to the Swiss city to help bridge differences and "move closer to an agreement." Russian Foreign Minister Sergei Lavrov had earlier joined the talks in a fresh push to clinch an interim deal that would curb some parts of Iran's nuclear work in exchange for sanctions relief.

A sticking point is Iran's insistence that its "right" to enrich uranium is recognised by the so-called P5+1 group of world powers, even though this is not explicitly set out in the nuclear Non-Proliferation Treaty.

"I neither confirm nor deny" that differences over the issue have been resolved "because the negotiations have not yet finalised," Mr Araqchi said.

Mr Araqchi, who later met with French negotiators in Geneva, was referring to reports in state media in Teheran that the P5+1 group had recognised Iran's "right" to enrich uranium.