Iran on Thursday warned global powers against making "excessive demands" in talks aimed at sealing a ground-breaking nuclear deal, after France demanded access to its military installations.

Iran on Thursday warned global powers against making "excessive demands" in talks aimed at sealing a ground-breaking nuclear deal, after France demanded access to its military installations.

"I would expect my negotiating partners to refrain from making excessive demands," Iranian Foreign Minister Mohammad Javad Zarif said during a visit to Athens, adding: "People need to have their foot in reality, not in illusions."

Zarif on Saturday is to meet US Secretary of State John Kerry in Geneva, after weeks of behind-the-scenes complex technical discussions in Vienna seeking to narrow the gaps on what would be an unprecedented deal on curtailing Iran's nuclear program.

Iran and the six global powers leading the talks -- Britain, China, France, Germany, Russia and the United States -- laid down a framework to guide the final accord in eight days of marathon late-night talks in Lausanne in early April.

The negotiators are working towards a proposed June 30 deadline for agreement.